Compiler/lexical analyzer: Difference between revisions
m (minor edits) |
m (Fix a bug in make-this-or-that-handler and use lisp keywords instead of obscure symbols.) |
||
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do (setf may-end (char= ch #\*))
finally (return (read stream t nil t))))
(t (make-token :name
(defun make-constant-handler (token-name)
Line 1,693:
(read-char stream nil nil t)
(make-token :name then :line line :column column))
(
(t
(lexer-error "Unrecognized character '~A'" next))))))
(defun identifier? (symbol)
Line 1,709 ⟶ 1,711:
(defun id->keyword (id line column)
(case id
(|if| (make-token :name
(|else| (make-token :name
(|while| (make-token :name
(|print| (make-token :name
(|putc| (make-token :name
(t nil)))
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(if (identifier? obj)
(or (id->keyword obj line column)
(make-token :name
(lexer-error "Invalid identifier name: ~A" obj))))))
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(let ((obj (read stream t nil t)))
(if (integerp obj)
(make-token :name
(lexer-error "Invalid integer: ~A" obj))))))
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(t ch))))
(if (char= #\' (read-char stream t nil t))
(make-token :name
(lexer-error "Only one character is allowed in character literal"))))
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(t ch)))
(vector-push-extend ch result)
finally (return (make-token :name
(defun make-lexer-readtable ()
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;; operators
(set-macro-character #\* (make-constant-handler
(set-macro-character #\/ #'handle-divide-or-comment)
(set-macro-character #\% (make-constant-handler
(set-macro-character #\+ (make-constant-handler
(set-macro-character #\- (make-constant-handler
(set-macro-character #\< (make-this-or-that-handler #\=
(set-macro-character #\> (make-this-or-that-handler #\=
(set-macro-character #\= (make-this-or-that-handler #\=
(set-macro-character #\! (make-this-or-that-handler #\=
(set-macro-character #\& (make-this-or-that-handler #\&
(set-macro-character #\| (make-this-or-that-handler #\|
;; symbols
(set-macro-character #\( (make-constant-handler
(set-macro-character #\) (make-constant-handler
(set-macro-character #\{ (make-constant-handler
(set-macro-character #\} (make-constant-handler
(set-macro-character #\; (make-constant-handler
(set-macro-character #\, (make-constant-handler
;; identifiers & keywords
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(token-line token) (token-column token) (token-name token) (token-value token))
finally (format t "~5D ~5D ~15A~%"
(line-of stream) (column-of stream)
(close stream))))
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(if file
(lex file)
(error "File must be specified"))))</lang>
{{out|case=test case 3}}
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=={{header|Euphoria}}==
|
Revision as of 16:50, 4 February 2017
You are encouraged to solve this task according to the task description, using any language you may know.
Lexical Analyzer
Definition from Wikipedia:
- Lexical analysis is the process of converting a sequence of characters (such as in a computer program or web page) into a sequence of tokens (strings with an identified "meaning"). A program that performs lexical analysis may be called a lexer, tokenizer, or scanner (though "scanner" is also used to refer to the first stage of a lexer).
Create a lexical analyzer for the simple programming language specified below. The program should read input from a file and/or stdin, and write output to a file and/or stdout. If the language being used has a lexer module/library/class, it would be great if two versions of the solution are provided: One without the lexer module, and one with.
The simple programming language to be analyzed is more or less a subset of C. It supports the following tokens:
- Operators
Name | Common name | Character sequence |
---|---|---|
Op_multiply | multiply | * |
Op_divide | divide | / |
Op_mod | mod | % |
Op_add | plus | + |
Op_subtract | minus | - |
Op_negate | unary minus | - |
Op_less | less than | < |
Op_lessequal | less than or equal | <= |
Op_greater | greater than | > |
Op_greaterequal | greater than or equal | >= |
Op_equal | equal | == |
Op_notequal | not equal | != |
Op_not | unary not | ! |
Op_assign | assignment | = |
Op_and | logical and | && |
Op_or | logical or | ¦¦ |
- The
-
token should always be interpreted as Op_subtract by the lexer. Turning some Op_subtract into Op_negate will be the job of the syntax analyzer, which is not part of this task.
- Symbols
Name | Common name | Character |
---|---|---|
LeftParen | left parenthesis | ( |
RightParen | right parenthesis | ) |
LeftBrace | left brace | { |
RightBrace | right brace | } |
Semicolon | semi-colon | ; |
Comma | comma | , |
- Keywords
Name | Character sequence |
---|---|
Keyword_if | if |
Keyword_else | else |
Keyword_while | while |
Keyword_print | |
Keyword_putc | putc |
- Identifiers and literals
These differ from the the previous tokens, in that each occurrence of them has a value associated with it.
Name | Common name | Format description | Format regex | Value |
---|---|---|---|---|
Identifier | identifier | one or more letter/number/underscore characters, but not starting with a number | [_a-zA-Z][_a-zA-Z0-9]*
|
as is |
Integer | integer literal | one or more digits | [0-9]+
|
as is, interpreted as a number |
Integer | char literal | exactly one character (anything except newline or single quote) or one of the allowed escape sequences, enclosed by single quotes | '([^'\n]|\\n|\\\\)'
|
the ASCII code point number of the character, e.g. 65 for 'A' and 10 for '\n'
|
String | string literal | zero or more characters (anything except newline or double quote), enclosed by double quotes | "[^"\n]*"
|
the characters without the double quotes and with escape sequences converted |
- For char and string literals, the
\n
escape sequence is supported to represent a new-line character. - For char and string literals, to represent a backslash, use
\\
. - No other special sequences are supported. This means that:
- Char literals cannot represent a single quote character (value 39).
- String literals cannot represent strings containing double quote characters.
- Zero-width tokens
Name | Location |
---|---|
End_of_input | when the end of the input stream is reached |
- White space
- Zero or more whitespace characters, or comments enclosed in
/* ... */
, are allowed between any two tokens, with the exceptions noted below. - "Longest token matching" is used to resolve conflicts (e.g., in order to match <= as a single token rather than the two tokens < and =).
- Whitespace is required between two tokens that have an alphanumeric character or underscore at the edge.
- This means: keywords, identifiers, and integer literals.
- e.g.
ifprint
is recognized as an identifier, instead of the keywords if and print. - e.g.
42fred
is invalid, and neither recognized as a number nor an identifier.
- Whitespace is not allowed inside of tokens (except for chars and strings where they are part of the value).
- e.g.
& &
is invalid, and not interpreted as the && operator.
- e.g.
For example, the following two program fragments are equivalent, and should produce the same token stream except for the line and column positions:
- <lang c>if ( p /* meaning n is prime */ ) {
print ( n , " " ) ; count = count + 1 ; /* number of primes found so far */
}</lang>
- <lang c>if(p){print(n," ");count=count+1;}</lang>
- Complete list of token names
End_of_input Op_multiply Op_divide Op_mod Op_add Op_subtract Op_negate Op_not Op_less Op_lessequal Op_greater Op_greaterequal Op_equal Op_notequal Op_assign Op_and Op_or Keyword_if Keyword_else Keyword_while Keyword_print Keyword_putc LeftParen RightParen LeftBrace RightBrace Semicolon Comma Identifier Integer String
The program output should be a sequence of lines, each consisting of the following whitespace-separated fields:
- the line number where the token starts
- the column number where the token starts
- the token name
- the token value (only for Identifier, Integer, and String tokens)
- the number of spaces between fields is up to you. Neatly aligned is nice, but not a requirement.
The following error conditions should be caught:
Error | Example |
---|---|
Empty character constant | ''
|
Unknown escape sequence. | \r
|
Multi-character constant. | 'xx'
|
End-of-file in comment. Closing comment characters not found. | |
End-of-file while scanning string literal. Closing string character not found. | |
End-of-line while scanning string literal. Closing string character not found before end-of-line. | |
Unrecognized character. | |
Invalid number. Starts like a number, but ends in non-numeric characters. | 123abc
|
Input | Output |
---|---|
Test Case 1: <lang c>/* Hello world */ print("Hello, World!\n");</lang> |
4 1 Keyword_print 4 6 LeftParen 4 7 String "Hello, World!\n" 4 24 RightParen 4 25 Semicolon 5 1 End_of_input |
Test Case 2: <lang c>/* Show Ident and Integers */ phoenix_number = 142857; print(phoenix_number, "\n");</lang> |
4 1 Identifier phoenix_number 4 16 Op_assign 4 18 Integer 142857 4 24 Semicolon 5 1 Keyword_print 5 6 LeftParen 5 7 Identifier phoenix_number 5 21 Comma 5 23 String "\n" 5 27 RightParen 5 28 Semicolon 6 1 End_of_input |
Test Case 3: <lang c>/* All lexical tokens - not syntactically correct, but that will have to wait until syntax analysis */ /* Print */ print /* Sub */ - /* Putc */ putc /* Lss */ < /* If */ if /* Gtr */ > /* Else */ else /* Leq */ <= /* While */ while /* Geq */ >= /* Lbrace */ { /* Eq */ == /* Rbrace */ } /* Neq */ != /* Lparen */ ( /* And */ && /* Rparen */ ) /* Or */ || /* Uminus */ - /* Semi */ ; /* Not */ ! /* Comma */ , /* Mul */ * /* Assign */ = /* Div */ / /* Integer */ 42 /* Mod */ % /* String */ "String literal" /* Add */ + /* Ident */ variable_name /* character literal */ '\n' /* character literal */ '\\' /* character literal */ ' '</lang> |
5 16 Keyword_print 5 40 Op_subtract 6 16 Keyword_putc 6 40 Op_less 7 16 Keyword_if 7 40 Op_greater 8 16 Keyword_else 8 40 Op_lessequal 9 16 Keyword_while 9 40 Op_greaterequal 10 16 LeftBrace 10 40 Op_equal 11 16 RightBrace 11 40 Op_notequal 12 16 LeftParen 12 40 Op_and 13 16 RightParen 13 40 Op_or 14 16 Op_subtract 14 40 Semicolon 15 16 Op_not 15 40 Comma 16 16 Op_multiply 16 40 Op_assign 17 16 Op_divide 17 40 Integer 42 18 16 Op_mod 18 40 String "String literal" 19 16 Op_add 19 40 Identifier variable_name 20 26 Integer 10 21 26 Integer 92 22 26 Integer 32 23 1 End_of_input |
Test Case 4: <lang c>/*** test printing, embedded \n and comments with lots of '*' ***/ print(42); print("\nHello World\nGood Bye\nok\n"); print("Print a slash n - \\n.\n");</lang> |
2 1 Keyword_print 2 6 LeftParen 2 7 Integer 42 2 9 RightParen 2 10 Semicolon 3 1 Keyword_print 3 6 LeftParen 3 7 String "\nHello World\nGood Bye\nok\n" 3 38 RightParen 3 39 Semicolon 4 1 Keyword_print 4 6 LeftParen 4 7 String "Print a slash n - \\n.\n" 4 33 RightParen 4 34 Semicolon 5 1 End_of_input |
- Additional examples
Your solution should pass all the test cases above and the additional tests found Here.
The C and Python versions can be considered reference implementations.
- Related Tasks
ALGOL W
<lang algolw>begin
%lexical analyser % % Algol W strings are limited to 256 characters in length so we limit source lines % % and tokens to 256 characters %
integer lineNumber, columnNumber; string(256) line; string(256) tkValue; integer tkType, tkLine, tkColumn, tkLength, tkIntegerValue; logical tkTooLong; string(1) currChar; string(1) newlineChar;
integer LINE_WIDTH, MAX_TOKEN_LENGTH, MAXINTEGER_OVER_10, MAXINTEGER_MOD_10; integer tOp_multiply , tOp_divide , tOp_mod , tOp_add , tOp_subtract , tOp_negate , tOp_less , tOp_lessequal , tOp_greater , tOp_greaterequal , tOp_equal , tOp_notequal , tOp_not , tOp_assign , tOp_and , tOp_or , tLeftParen , tRightParen , tLeftBrace , tRightBrace , tSemicolon , tComma , tKeyword_if , tKeyword_else , tKeyword_while , tKeyword_print , tKeyword_putc , tIdentifier , tInteger , tString , tEnd_of_input , tComment ;
string(16) array tkName ( 1 :: 32 );
% reports an error % procedure lexError( string(80) value message ); begin integer errorPos; write( i_w := 1, s_w := 0, "**** Error at(", lineNumber, ",", columnNumber, "): " ); errorPos := 0; while errorPos < 80 and message( errorPos // 1 ) not = "." do begin writeon( s_w := 0, message( errorPos // 1 ) ); errorPos := errorPos + 1 end while_not_at_end_of_message ; writeon( s_w := 0, "." ) end lexError ;
% gets the next source character % procedure nextChar ; begin if columnNumber = LINE_WIDTH then begin currChar := newlineChar; columnNumber := columnNumber + 1 end else if columnNumber > LINE_WIDTH then begin readcard( line ); columnNumber := 1; if not XCPNOTED(ENDFILE) then lineNumber := lineNumber + 1; currChar := line( 0 // 1 ) end else begin currChar := line( columnNumber // 1 ); columnNumber := columnNumber + 1 end end nextChar ;
% gets the next token, returns the token type % integer procedure nextToken ; begin
% returns true if currChar is in the inclusive range lowerValue to upperValue % % false otherwise % logical procedure range( string(1) value lowerValue, upperValue ) ; begin currChar >= lowerValue and currChar <= upperValue end range ;
% returns true if the current character can start an identifier, false otherwise % logical procedure identifierStartChar ; begin currChar = "_" or range( "a", "z" ) or range( "A", "Z" ) end identifierStartChar ;
% add the current character to the token and get the next % procedure addAndNextChar ; begin if tkLength >= MAX_TOKEN_LENGTH then tkTooLong := true else begin tkValue( tkLength // 1 ) := currChar; tkLength := tkLength + 1 end if_symbol_not_too_long ; nextChar end % addAndNextChar % ;
% handle a single character token % procedure singleCharToken( integer value tokenType ) ; begin tkType := tokenType; nextChar end singleCharToken ;
% handle a doubled character token: && or || % procedure doubleCharToken( integer value tokenType ) ; begin string(1) firstChar; firstChar := currChar; tkType := tokenType; nextChar; if currChar = firstChar then nextChar else % the character wasn't doubled % lexError( "Unrecognised character." ); end singleCharToken ;
% handle an operator or operator= token % procedure opOrOpEqual( integer value opToken, opEqualToken ) ; begin tkType := opToken; nextChar; if currChar = "=" then begin % have operator= % tkType := opEqualToken; nextChar end if_currChar_is_equal ; end opOrOpEqual ;
% handle a / operator or /* comment % procedure divideOrComment ; begin tkType := tOp_divide; nextChar; if currChar = "*" then begin % have a comment % logical moreComment; tkType := tComment; moreComment := true; while moreComment do begin nextChar; while currChar not = "*" and not XCPNOTED(ENDFILE) do nextChar; while currChar = "*" and not XCPNOTED(ENDFILE) do nextChar; moreComment := ( currChar not = "/" and not XCPNOTED(ENDFILE) ) end while_more_comment ; if not XCPNOTED(ENDFILE) then nextChar else lexError( "End-of-file in comment." ) end if_currChar_is_star ; end divideOrComment ;
% handle an indentifier or keyword % procedure identifierOrKeyword ; begin tkType := tIdentifier; while identifierStartChar or range( "0", "9" ) do addAndNextChar; % there are only 5 keywords, so we just test each in turn here % if tkValue = "if" then tkType := tKeyword_if else if tkValue = "else" then tkType := tKeyword_else else if tkValue = "while" then tkType := tKeyword_while else if tkValue = "print" then tkType := tKeyword_print else if tkValue = "putc" then tkType := tKeyword_putc; if tkType not = tIdentifier then tkValue := ""; end identifierOrKeyword ;
% handle an integer literal % procedure integerLiteral ; begin logical overflowed; integer digit; overflowed := false; tkType := tInteger; while range( "0", "9" ) do begin digit := ( decode( currChar ) - decode( "0" ) ); if tkIntegerValue > MAXINTEGER_OVER_10 then overflowed := true else if tkIntegerValue = MAXINTEGER_OVER_10 and digit > MAXINTEGER_MOD_10 then overflowed := true else begin tkIntegerValue := tkIntegerValue * 10; tkIntegerValue := tkIntegerValue + digit; end; nextChar end while_have_a_digit ; if overflowed then lexError( "Number too large." ); if identifierStartChar then lexError( "Number followed by letter or underscore." ); end integerLiteral ;
% handle a char literal % procedure charLiteral ; begin nextChar; if currChar = "'" or currChar = newlineChar then lexError( "Invalid character constant." ) else if currChar = "\" then begin % have an escape % nextChar; if currChar = "n" then currChar := newlineChar else if currChar not = "\" then lexError( "Unknown escape sequence." ) end; tkType := tInteger; tkIntegerValue := decode( currChar ); % should have a closing quoute next % nextChar; if currChar not = "'" then lexError( "Multi-character constant." ) else nextChar end charLiteral ;
% handle a string literal % procedure stringLiteral ; begin tkType := tString; tkValue( 0 // 1 ) := currChar; tkLength := 1; nextChar; while currChar not = """" and currChar not = newlineChar and not XCPNOTED(ENDFILE) do addAndNextChar; if currChar = newlineChar then lexError( "End-of-line while scanning string literal." ) else if XCPNOTED(ENDFILE) then lexError( "End-of-file while scanning string literal." ) else % currChar must be """" % addAndNextChar end stringLiteral ;
while begin % skip white space % while ( currChar = " " or currChar = newlineChar ) and not XCPNOTED(ENDFILE) do nextChar; % get the token % tkLine := lineNumber; tkColumn := columnNumber; tkValue := ""; tkLength := 0; tkIntegerValue := 0; tkTooLong := false; if XCPNOTED(ENDFILE) then tkType := tEnd_of_input else if currChar = "*" then singleCharToken( tOp_multiply ) else if currChar = "/" then divideOrComment else if currChar = "%" then singleCharToken( tOp_mod ) else if currChar = "+" then singleCharToken( tOp_add ) else if currChar = "-" then singleCharToken( tOp_subtract ) else if currChar = "<" then opOrOpEqual( tOp_less, tOp_lessequal ) else if currChar = ">" then opOrOpEqual( tOp_greater, tOp_greaterequal ) else if currChar = "=" then opOrOpEqual( tOp_assign, tOp_equal ) else if currChar = "!" then opOrOpEqual( tOp_not, tOp_notequal ) else if currChar = "&" then doubleCharToken( tOp_and ) else if currChar = "|" then doubleCharToken( tOp_or ) else if currChar = "(" then singleCharToken( tLeftParen ) else if currChar = ")" then singleCharToken( tRightParen ) else if currChar = "{" then singleCharToken( tLeftBrace ) else if currChar = "}" then singleCharToken( tRightBrace ) else if currChar = ";" then singleCharToken( tSemicolon ) else if currChar = "," then singleCharToken( tComma ) else if identifierStartChar then identifierOrKeyword else if range( "0", "9" ) then integerLiteral else if currChar = "'" then charLiteral else if currChar = """" then stringLiteral else begin lexError( "Unrecognised character." ); singleCharToken( tComment ) end ; % continue until we get something other than a comment % tkType = tComment end do begin end; if tkTooLong then if tkType = tString then lexError( "String literal too long." ) else lexError( "Identifier too long." ); tkType end nextToken ;
% outputs the current token % procedure writeToken ; begin write( i_w := 5, s_w := 2, tkLine, tkColumn, tkName( tkType ) ); if tkType = tInteger then writeon( i_w := 11, tkIntegerValue ) else if tkLength > 0 then begin writeon( " " ); for tkPos := 0 until tkLength - 1 do writeon( s_w := 0, tkValue( tkPos // 1 ) ); end end writeToken ;
LINE_WIDTH := 256; MAXINTEGER_MOD_10 := MAXINTEGER rem 10; MAX_TOKEN_LENGTH := 256; MAXINTEGER_OVER_10 := MAXINTEGER div 10; newlineChar := code( 10 ); tOp_multiply := 1; tkName( tOp_multiply ) := "Op_multiply"; tOp_divide := 2; tkName( tOp_divide ) := "Op_divide"; tOp_mod := 3; tkName( tOp_mod ) := "Op_mod"; tOp_add := 4; tkName( tOp_add ) := "Op_add"; tOp_subtract := 5; tkName( tOp_subtract ) := "Op_subtract"; tOp_negate := 6; tkName( tOp_negate ) := "Op_negate"; tOp_less := 7; tkName( tOp_less ) := "Op_less"; tOp_lessequal := 8; tkName( tOp_lessequal ) := "Op_lessequal"; tOp_greater := 9; tkName( tOp_greater ) := "Op_greater"; tOp_greaterequal := 10; tkName( tOp_greaterequal ) := "Op_greaterequal"; tOp_equal := 11; tkName( tOp_equal ) := "Op_equal"; tOp_notequal := 12; tkName( tOp_notequal ) := "Op_notequal"; tOp_not := 13; tkName( tOp_not ) := "Op_not"; tOp_assign := 14; tkName( tOp_assign ) := "Op_assign"; tOp_and := 15; tkName( tOp_and ) := "Op_and"; tOp_or := 16; tkName( tOp_or ) := "Op_or"; tLeftParen := 17; tkName( tLeftParen ) := "LeftParen"; tRightParen := 18; tkName( tRightParen ) := "RightParen"; tLeftBrace := 19; tkName( tLeftBrace ) := "LeftBrace"; tRightBrace := 20; tkName( tRightBrace ) := "RightBrace"; tSemicolon := 21; tkName( tSemicolon ) := "Semicolon"; tComma := 22; tkName( tComma ) := "Comma"; tKeyword_if := 23; tkName( tKeyword_if ) := "Keyword_if"; tKeyword_else := 24; tkName( tKeyword_else ) := "Keyword_else"; tKeyword_while := 25; tkName( tKeyword_while ) := "Keyword_while"; tKeyword_print := 26; tkName( tKeyword_print ) := "Keyword_print"; tKeyword_putc := 27; tkName( tKeyword_putc ) := "Keyword_putc"; tIdentifier := 28; tkName( tIdentifier ) := "Identifier"; tInteger := 29; tkName( tInteger ) := "Integer"; tString := 30; tkName( tString ) := "String"; tEnd_of_input := 31; tkName( tEnd_of_input ) := "End_of_input"; tComment := 32; tkName( tComment ) := "Comment";
% allow the program to continue after reaching end-of-file % ENDFILE := EXCEPTION( false, 1, 0, false, "EOF" ); % ensure the first call to nextToken reads the first line % lineNumber := 0; columnNumber := LINE_WIDTH + 1; currChar := " "; % get and print all tokens from standard input % while nextToken not = tEnd_of_input do writeToken; writeToken
end.</lang>
- Output:
Test case 3
5 16 Keyword_print 5 40 Op_subtract 6 16 Keyword_putc 6 40 Op_less 7 16 Keyword_if 7 40 Op_greater 8 16 Keyword_else 8 40 Op_lessequal 9 16 Keyword_while 9 40 Op_greaterequal 10 16 LeftBrace 10 40 Op_equal 11 16 RightBrace 11 40 Op_notequal 12 16 LeftParen 12 40 Op_and 13 16 RightParen 13 40 Op_or 14 16 Op_subtract 14 40 Semicolon 15 16 Op_not 15 40 Comma 16 16 Op_multiply 16 40 Op_assign 17 16 Op_divide 17 40 Integer 42 18 16 Op_mod 18 40 String "String literal" 19 16 Op_add 19 40 Identifier variable_name 20 26 Integer 10 21 26 Integer 92 22 26 Integer 32 23 1 End_of_input
AWK
Tested with gawk 4.1.1 and mawk 1.3.4. <lang AWK> BEGIN {
all_syms["tk_EOI" ] = "End_of_input" all_syms["tk_Mul" ] = "Op_multiply" all_syms["tk_Div" ] = "Op_divide" all_syms["tk_Mod" ] = "Op_mod" all_syms["tk_Add" ] = "Op_add" all_syms["tk_Sub" ] = "Op_subtract" all_syms["tk_Negate" ] = "Op_negate" all_syms["tk_Not" ] = "Op_not" all_syms["tk_Lss" ] = "Op_less" all_syms["tk_Leq" ] = "Op_lessequal" all_syms["tk_Gtr" ] = "Op_greater" all_syms["tk_Geq" ] = "Op_greaterequal" all_syms["tk_Eq" ] = "Op_equal" all_syms["tk_Neq" ] = "Op_notequal" all_syms["tk_Assign" ] = "Op_assign" all_syms["tk_And" ] = "Op_and" all_syms["tk_Or" ] = "Op_or" all_syms["tk_If" ] = "Keyword_if" all_syms["tk_Else" ] = "Keyword_else" all_syms["tk_While" ] = "Keyword_while" all_syms["tk_Print" ] = "Keyword_print" all_syms["tk_Putc" ] = "Keyword_putc" all_syms["tk_Lparen" ] = "LeftParen" all_syms["tk_Rparen" ] = "RightParen" all_syms["tk_Lbrace" ] = "LeftBrace" all_syms["tk_Rbrace" ] = "RightBrace" all_syms["tk_Semi" ] = "Semicolon" all_syms["tk_Comma" ] = "Comma" all_syms["tk_Ident" ] = "Identifier" all_syms["tk_Integer"] = "Integer" all_syms["tk_String" ] = "String"
## single character only symbols symbols["{" ] = "tk_Lbrace" symbols["}" ] = "tk_Rbrace" symbols["(" ] = "tk_Lparen" symbols[")" ] = "tk_Rparen" symbols["+" ] = "tk_Add" symbols["-" ] = "tk_Sub" symbols["*" ] = "tk_Mul" symbols["%" ] = "tk_Mod" symbols[";" ] = "tk_Semi" symbols["," ] = "tk_Comma"
key_words["if" ] = "tk_If" key_words["else" ] = "tk_Else" key_words["print"] = "tk_Print" key_words["putc" ] = "tk_Putc" key_words["while"] = "tk_While"
# Set up an array that emulates the ord() function. for(n=0;n<256;n++) ord[sprintf("%c",n)]=n
input_file = "-" if (ARGC > 1) input_file = ARGV[1] RS=FS="" # read complete file into one line $0 getline < input_file the_ch = " " # dummy first char - but it must be a space the_col = 0 # always points to the current character the_line = 1 for (the_nf=1; ; ) { split(gettok(), t, SUBSEP) printf("%5s %5s %-14s", t[2], t[3], all_syms[t[1]]) if (t[1] == "tk_Integer") printf(" %5s\n", t[4]) else if (t[1] == "tk_Ident" ) printf(" %s\n", t[4]) else if (t[1] == "tk_String" ) printf(" \"%s\"\n", t[4]) else print("") if (t[1] == "tk_EOI") break }
}
- show error and exit
function error(line, col, msg) {
print(line, col, msg) exit(1)
}
- get the next character from the input
function next_ch() {
the_ch = $the_nf the_nf ++ the_col ++ if (the_ch == "\n") { the_line ++ the_col = 0 } return the_ch
}
- 'x' - character constants
function char_lit(err_line, err_col) {
n = ord[next_ch()] # skip opening quote if (the_ch == "'") { error(err_line, err_col, "empty character constant") } else if (the_ch == "\\") { next_ch() if (the_ch == "n") n = 10 else if (the_ch == "\\") n = ord["\\"] else error(err_line, err_col, "unknown escape sequence " the_ch) } if (next_ch() != "'") error(err_line, err_col, "multi-character constant") next_ch() return "tk_Integer" SUBSEP err_line SUBSEP err_col SUBSEP n
}
- process divide or comments
function div_or_cmt(err_line, err_col) {
if (next_ch() != "*") return "tk_Div" SUBSEP err_line SUBSEP err_col # comment found next_ch() while (1) { if (the_ch == "*") { if (next_ch() == "/") { next_ch() return gettok() } else if (the_ch == "") { error(err_line, err_col, "EOF in comment") } } else { next_ch() } }
}
- "string"
function string_lit(start, err_line, err_col) {
text = "" while (next_ch() != start) { if (the_ch == "") error(err_line, err_col, "EOF while scanning string literal") if (the_ch == "\n") error(err_line, err_col, "EOL while scanning string literal") text = text the_ch } next_ch() return "tk_String" SUBSEP err_line SUBSEP err_col SUBSEP text
}
- handle identifiers and integers
function ident_or_int(err_line, err_col) {
is_number = 1 text = "" while ((the_ch ~ /^[0-9a-zA-Z]+$/) || (the_ch == "_")) { text = text the_ch if (! (the_ch ~ /^[0-9]+$/)) is_number = 0 next_ch() } if (text == "") error(err_line, err_col, "ident_or_int: unrecognized character: " the_ch) if (text ~ /^[0-9]/) { if (! is_number) error(err_line, err_col, "invalid number: " text) n = text + 0 return "tk_Integer" SUBSEP err_line SUBSEP err_col SUBSEP n } if (text in key_words) return key_words[text] SUBSEP err_line SUBSEP err_col return "tk_Ident" SUBSEP err_line SUBSEP err_col SUBSEP text
}
- look ahead for '>=', etc.
function follow(expect, ifyes, ifno, err_line, err_col) {
if (next_ch() == expect) { next_ch() return ifyes SUBSEP err_line SUBSEP err_col } if (ifno == tk_EOI) error(err_line, err_col, "follow: unrecognized character: " the_ch) return ifno SUBSEP err_line SUBSEP err_col
}
- return the next token type
function gettok() {
while (the_ch == " " || the_ch == "\n" || the_ch == "\r") next_ch() err_line = the_line err_col = the_col if (the_ch == "" ) return "tk_EOI" SUBSEP err_line SUBSEP err_col else if (the_ch == "/") return div_or_cmt(err_line, err_col) else if (the_ch == "'") return char_lit(err_line, err_col) else if (the_ch == "<") return follow("=", "tk_Leq", "tk_Lss", err_line, err_col) else if (the_ch == ">") return follow("=", "tk_Geq", "tk_Gtr", err_line, err_col) else if (the_ch == "=") return follow("=", "tk_Eq", "tk_Assign", err_line, err_col) else if (the_ch == "!") return follow("=", "tk_Neq", "tk_Not", err_line, err_col) else if (the_ch == "&") return follow("&", "tk_And", "tk_EOI", err_line, err_col) else if (the_ch == "|") return follow("|", "tk_Or", "tk_EOI", err_line, err_col) else if (the_ch =="\"") return string_lit(the_ch, err_line, err_col) else if (the_ch in symbols) { sym = symbols[the_ch] next_ch() return sym SUBSEP err_line SUBSEP err_col } else { return ident_or_int(err_line, err_col) }
} </lang>
- Output — count:
1 1 Identifier count 1 7 Op_assign 1 9 Integer 1 1 10 Semicolon 2 1 Keyword_while 2 7 LeftParen 2 8 Identifier count 2 14 Op_less 2 16 Integer 10 2 18 RightParen 2 20 LeftBrace 3 5 Keyword_print 3 10 LeftParen 3 11 String "count is: " 3 23 Comma 3 25 Identifier count 3 30 Comma 3 32 String "\n" 3 36 RightParen 3 37 Semicolon 4 5 Identifier count 4 11 Op_assign 4 13 Identifier count 4 19 Op_add 4 21 Integer 1 4 22 Semicolon 5 1 RightBrace 5 3 End_of_input
C
Tested with gcc 4.81 and later, compiles warning free with -Wall -Wextra <lang C>#include <stdlib.h>
- include <stdio.h>
- include <stdarg.h>
- include <ctype.h>
- include <string.h>
- include <errno.h>
- include <stdbool.h>
- include <limits.h>
- define NELEMS(arr) (sizeof(arr) / sizeof(arr[0]))
- define da_dim(name, type) type *name = NULL; \
int _qy_ ## name ## _p = 0; \ int _qy_ ## name ## _max = 0
- define da_rewind(name) _qy_ ## name ## _p = 0
- define da_redim(name) do {if (_qy_ ## name ## _p >= _qy_ ## name ## _max) \
name = realloc(name, (_qy_ ## name ## _max += 32) * sizeof(name[0]));} while (0)
- define da_append(name, x) do {da_redim(name); name[_qy_ ## name ## _p++] = x;} while (0)
- define da_len(name) _qy_ ## name ## _p
typedef enum {
tk_EOI, tk_Mul, tk_Div, tk_Mod, tk_Add, tk_Sub, tk_Negate, tk_Not, tk_Lss, tk_Leq, tk_Gtr, tk_Geq, tk_Eq, tk_Neq, tk_Assign, tk_And, tk_Or, tk_If, tk_Else, tk_While, tk_Print, tk_Putc, tk_Lparen, tk_Rparen, tk_Lbrace, tk_Rbrace, tk_Semi, tk_Comma, tk_Ident, tk_Integer, tk_String
} TokenType;
typedef struct {
TokenType tok; int err_ln, err_col; union { int n; /* value for constants */ char *text; /* text for idents */ };
} tok_s;
static FILE *source_fp, *dest_fp; static int line = 1, col = 0, the_ch = ' '; da_dim(text, char);
tok_s gettok();
static void error(int err_line, int err_col, const char *fmt, ... ) {
char buf[1000]; va_list ap;
va_start(ap, fmt); vsprintf(buf, fmt, ap); va_end(ap); printf("(%d,%d) error: %s\n", err_line, err_col, buf); exit(1);
}
static int next_ch() { /* get next char from input */
the_ch = getc(source_fp); ++col; if (the_ch == '\n') { ++line; col = 0; } return the_ch;
}
static tok_s char_lit(int n, int err_line, int err_col) { /* 'x' */
if (the_ch == '\) error(err_line, err_col, "gettok: empty character constant"); if (the_ch == '\\') { next_ch(); if (the_ch == 'n') n = 10; else if (the_ch == '\\') n = '\\'; else error(err_line, err_col, "gettok: unknown escape sequence \\%c", the_ch); } if (next_ch() != '\) error(err_line, err_col, "multi-character constant"); next_ch(); return (tok_s){tk_Integer, err_line, err_col, {n}};
}
static tok_s div_or_cmt(int err_line, int err_col) { /* process divide or comments */
if (the_ch != '*') return (tok_s){tk_Div, err_line, err_col, {0}};
/* comment found */ next_ch(); for (;;) { if (the_ch == '*') { if (next_ch() == '/') { next_ch(); return gettok(); } } else if (the_ch == EOF) error(err_line, err_col, "EOF in comment"); else next_ch(); }
}
static tok_s string_lit(int start, int err_line, int err_col) { /* "st" */
da_rewind(text);
while (next_ch() != start) { if (the_ch == '\n') error(err_line, err_col, "EOL in string"); if (the_ch == EOF) error(err_line, err_col, "EOF in string"); da_append(text, (char)the_ch); } da_append(text, '\0');
next_ch(); return (tok_s){tk_String, err_line, err_col, {.text=text}};
}
static int kwd_cmp(const void *p1, const void *p2) {
return strcmp(*(char **)p1, *(char **)p2);
}
static TokenType get_ident_type(const char *ident) {
static struct { char *s; TokenType sym; } kwds[] = { {"else", tk_Else}, {"if", tk_If}, {"print", tk_Print}, {"putc", tk_Putc}, {"while", tk_While}, }, *kwp;
return (kwp = bsearch(&ident, kwds, NELEMS(kwds), sizeof(kwds[0]), kwd_cmp)) == NULL ? tk_Ident : kwp->sym;
}
static tok_s ident_or_int(int err_line, int err_col) {
int n, is_number = true;
da_rewind(text); while (isalnum(the_ch) || the_ch == '_') { da_append(text, (char)the_ch); if (!isdigit(the_ch)) is_number = false; next_ch(); } if (da_len(text) == 0) error(err_line, err_col, "gettok: unrecognized character (%d) '%c'\n", the_ch, the_ch); da_append(text, '\0'); if (isdigit(text[0])) { if (!is_number) error(err_line, err_col, "invalid number: %s\n", text); n = strtol(text, NULL, 0); if (n == LONG_MAX && errno == ERANGE) error(err_line, err_col, "Number exceeds maximum value"); return (tok_s){tk_Integer, err_line, err_col, {n}}; } return (tok_s){get_ident_type(text), err_line, err_col, {.text=text}};
}
static tok_s follow(int expect, TokenType ifyes, TokenType ifno, int err_line, int err_col) { /* look ahead for '>=', etc. */
if (the_ch == expect) { next_ch(); return (tok_s){ifyes, err_line, err_col, {0}}; } if (ifno == tk_EOI) error(err_line, err_col, "follow: unrecognized character '%c' (%d)\n", the_ch, the_ch); return (tok_s){ifno, err_line, err_col, {0}};
}
tok_s gettok() { /* return the token type */
/* skip white space */ while (isspace(the_ch)) next_ch(); int err_line = line; int err_col = col; switch (the_ch) { case '{': next_ch(); return (tok_s){tk_Lbrace, err_line, err_col, {0}}; case '}': next_ch(); return (tok_s){tk_Rbrace, err_line, err_col, {0}}; case '(': next_ch(); return (tok_s){tk_Lparen, err_line, err_col, {0}}; case ')': next_ch(); return (tok_s){tk_Rparen, err_line, err_col, {0}}; case '+': next_ch(); return (tok_s){tk_Add, err_line, err_col, {0}}; case '-': next_ch(); return (tok_s){tk_Sub, err_line, err_col, {0}}; case '*': next_ch(); return (tok_s){tk_Mul, err_line, err_col, {0}}; case '%': next_ch(); return (tok_s){tk_Mod, err_line, err_col, {0}}; case ';': next_ch(); return (tok_s){tk_Semi, err_line, err_col, {0}}; case ',': next_ch(); return (tok_s){tk_Comma,err_line, err_col, {0}}; case '/': next_ch(); return div_or_cmt(err_line, err_col); case '\: next_ch(); return char_lit(the_ch, err_line, err_col); case '<': next_ch(); return follow('=', tk_Leq, tk_Lss, err_line, err_col); case '>': next_ch(); return follow('=', tk_Geq, tk_Gtr, err_line, err_col); case '=': next_ch(); return follow('=', tk_Eq, tk_Assign, err_line, err_col); case '!': next_ch(); return follow('=', tk_Neq, tk_Not, err_line, err_col); case '&': next_ch(); return follow('&', tk_And, tk_EOI, err_line, err_col); case '|': next_ch(); return follow('|', tk_Or, tk_EOI, err_line, err_col); case '"' : return string_lit(the_ch, err_line, err_col); default: return ident_or_int(err_line, err_col); case EOF: return (tok_s){tk_EOI, err_line, err_col, {0}}; }
}
void run() { /* tokenize the given input */
tok_s tok; do { tok = gettok(); fprintf(dest_fp, "%5d %5d %.15s", tok.err_ln, tok.err_col, &"End_of_input Op_multiply Op_divide Op_mod Op_add " "Op_subtract Op_negate Op_not Op_less Op_lessequal " "Op_greater Op_greaterequal Op_equal Op_notequal Op_assign " "Op_and Op_or Keyword_if Keyword_else Keyword_while " "Keyword_print Keyword_putc LeftParen RightParen LeftBrace " "RightBrace Semicolon Comma Identifier Integer " "String " [tok.tok * 16]); if (tok.tok == tk_Integer) fprintf(dest_fp, " %4d", tok.n); else if (tok.tok == tk_Ident) fprintf(dest_fp, " %s", tok.text); else if (tok.tok == tk_String) fprintf(dest_fp, " \"%s\"", tok.text); fprintf(dest_fp, "\n"); } while (tok.tok != tk_EOI); if (dest_fp != stdout) fclose(dest_fp);
}
void init_io(FILE **fp, FILE *std, const char mode[], const char fn[]) {
if (fn[0] == '\0') *fp = std; else if ((*fp = fopen(fn, mode)) == NULL) error(0, 0, "Can't open %s\n", fn);
}
int main(int argc, char *argv[]) {
init_io(&source_fp, stdin, "r", argc > 1 ? argv[1] : ""); init_io(&dest_fp, stdout, "wb", argc > 2 ? argv[2] : ""); run(); return 0;
}</lang>
- Output — test case 3:
5 16 Keyword_print 5 40 Op_subtract 6 16 Keyword_putc 6 40 Op_less 7 16 Keyword_if 7 40 Op_greater 8 16 Keyword_else 8 40 Op_lessequal 9 16 Keyword_while 9 40 Op_greaterequal 10 16 LeftBrace 10 40 Op_equal 11 16 RightBrace 11 40 Op_notequal 12 16 LeftParen 12 40 Op_and 13 16 RightParen 13 40 Op_or 14 16 Op_subtract 14 40 Semicolon 15 16 Op_not 15 40 Comma 16 16 Op_multiply 16 40 Op_assign 17 16 Op_divide 17 40 Integer 42 18 16 Op_mod 18 40 String "String literal" 19 16 Op_add 19 40 Identifier variable_name 20 26 Integer 10 21 26 Integer 92 22 26 Integer 32 23 1 End_of_input
C#
Requires C#6.0 because of the use of null coalescing operators. <lang csharp> using System; using System.IO; using System.Linq; using System.Collections.Generic;
namespace Rosetta {
public enum TokenType { End_of_input, Op_multiply, Op_divide, Op_mod, Op_add, Op_subtract, Op_negate, Op_not, Op_less, Op_lessequal, Op_greater, Op_greaterequal, Op_equal, Op_notequal, Op_assign, Op_and, Op_or, Keyword_if, Keyword_else, Keyword_while, Keyword_print, Keyword_putc, LeftParen, RightParen, LeftBrace, RightBrace, Semicolon, Comma, Identifier, Integer, String, None }
/// <summary> /// Storage class for tokens /// </summary> public class Token { public TokenType Type { get; set; } public int Line { get; set; } public int Position { get; set; } public string Value { get; set; } public override string ToString() { if (Type == TokenType.Integer || Type == TokenType.Identifier) { return String.Format("{0,-5} {1,-5} {2,-14} {3}", Line, Position, Type.ToString(), Value); } else if (Type == TokenType.String) { return String.Format("{0,-5} {1,-5} {2,-14} \"{3}\"", Line, Position, Type.ToString(), Value.Replace("\n", "\\n")); } return String.Format("{0,-5} {1,-5} {2,-14}", Line, Position, Type.ToString()); } }
/// <summary> /// C# Example of Lexical scanner for Rosetta Compiler /// </summary> public class LexicalScanner {
// character classes private const string _letters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_"; private const string _numbers = "0123456789"; private const string _identifier = _letters + _numbers + "_"; private const string _whitespace = " \t\n\r"; // mappings from string keywords to token type private Dictionary<string, TokenType> _keywordTokenTypeMap = new Dictionary<string, TokenType>() { { "if", TokenType.Keyword_if }, { "else", TokenType.Keyword_else }, { "while", TokenType.Keyword_while }, { "print", TokenType.Keyword_print }, { "putc", TokenType.Keyword_putc } };
// mappings from simple operators to token type private Dictionary<string, TokenType> _operatorTokenTypeMap = new Dictionary<string, TokenType>() { { "+", TokenType.Op_add }, { "-", TokenType.Op_subtract }, { "*", TokenType.Op_multiply }, { "/", TokenType.Op_divide }, { "%", TokenType.Op_mod }, { "=", TokenType.Op_assign }, { "<", TokenType.Op_less }, { ">", TokenType.Op_greater }, { "!", TokenType.Op_not }, };
private List<string> _keywords; private string _operators = "+-*/%=<>!%";
private string _code; private List<Token> tokens = new List<Token>();
private int _line = 1; private int _position = 1;
public string CurrentCharacter { get { try { return _code.Substring(0, 1); } catch (ArgumentOutOfRangeException) { return ""; } } }
/// <summary> /// Lexical scanner initialiser /// </summary> /// <param name="code">Code to be tokenised</param> public LexicalScanner (string code) { _code = code; _keywords = _keywordTokenTypeMap.Keys.ToList(); }
/// <summary> /// Advance the cursor forward given number of characters /// </summary> /// <param name="characters">Number of characters to advance</param> private void advance(int characters=1) { try { // reset position when there is a newline if (CurrentCharacter == "\n") { _position = 0; _line++; } _code = _code.Substring(characters, _code.Length - characters); _position += characters; } catch (ArgumentOutOfRangeException) { _code = ""; } }
/// <summary> /// Outputs error message to the console and exits /// </summary> /// <param name="message">Error message to display to user</param> /// <param name="line">Line error occurred on</param> /// <param name="position">Line column that the error occurred at</param> public void error(string message, int line, int position) { // output error to the console and exit Console.WriteLine(String.Format("{0} @ {1}:{2}", message, line, position)); Environment.Exit(1); }
/// <summary> /// Pattern matching using first & follow matching /// </summary> /// <param name="recogniseClass">String of characters that identifies the token type /// or the exact match the be made if exact:true</param> /// <param name="matchClass">String of characters to match against remaining target characters</param> /// <param name="tokenType">Type of token the match represents.</param> /// <param name="notNextClass">Optional class of characters that cannot follow the match</param> /// <param name="maxLen">Optional maximum length of token value</param> /// <param name="exact">Denotes whether recogniseClass represents an exact match or class match. /// Default: false</param> /// <param name="discard">Denotes whether the token is kept or discarded. Default: false</param> /// <param name="offset">Optiona line position offset to account for discarded tokens</param> /// <returns>Boolean indicating if a match was made </returns> public bool match(string recogniseClass, string matchClass, TokenType tokenType, string notNextClass=null, int maxLen=Int32.MaxValue, bool exact=false, bool discard=false, int offset=0) {
// if we've hit the end of the file, there's no more matching to be done if (CurrentCharacter == "") return false;
// store _current_ line and position so that our vectors point at the start // of each token int line = _line; int position = _position;
// special case exact tokens to avoid needing to worry about backtracking if (exact) { if (_code.StartsWith(recogniseClass)) { if (!discard) tokens.Add(new Token() { Type = tokenType, Value = recogniseClass, Line = line, Position = position - offset}); advance(recogniseClass.Length); return true; } return false; }
// first match - denotes the token type usually if (!recogniseClass.Contains(CurrentCharacter)) return false;
string tokenValue = CurrentCharacter; advance();
// follow match while we haven't exceeded maxLen and there are still characters // in the code stream while ((matchClass ?? "").Contains(CurrentCharacter) && tokenValue.Length <= maxLen && CurrentCharacter != "") { tokenValue += CurrentCharacter; advance(); }
// ensure that any incompatible characters are not next to the token // eg 42fred is invalid, and neither recognized as a number nor an identifier. // _letters would be the notNextClass if (notNextClass != null && notNextClass.Contains(CurrentCharacter)) error("Unrecognised character: " + CurrentCharacter, _line, _position);
// only add tokens to the stack that aren't marked as discard - dont want // things like open and close quotes/comments if (!discard) { Token token = new Token() { Type = tokenType, Value = tokenValue, Line = line, Position = position - offset }; tokens.Add(token); }
return true; }
/// <summary> /// Tokenise the input code /// </summary> /// <returns>List of Tokens</returns> public List<Token> scan() {
while (CurrentCharacter != "") { // match whitespace match(_whitespace, _whitespace, TokenType.None, discard: true);
// match integers match(_numbers, _numbers, TokenType.Integer, notNextClass:_letters); // match identifiers and keywords if (match(_letters, _identifier, TokenType.Identifier)) { Token match = tokens.Last(); if (_keywords.Contains(match.Value)) match.Type = _keywordTokenTypeMap[match.Value]; }
// match string similarly to comments without allowing newlines // this token doesn't get discarded though if (match("\"", null, TokenType.String, discard:true)) { string value = ""; int position = _position; while (!match("\"", null, TokenType.String, discard:true)) { // not allowed newlines in strings if (CurrentCharacter == "\n") error("End-of-line while scanning string literal. Closing string character not found before end-of-line", _line, _position); // end of file reached before finding end of string if (CurrentCharacter == "") error("End-of-file while scanning string literal. Closing string character not found", _line, _position);
value += CurrentCharacter;
// deal with escape sequences - we only accept newline (\n) if (value.Length >= 2) { string lastCharacters = value.Substring(value.Length - 2, 2); if (lastCharacters[0] == '\\') { if (lastCharacters[1] != 'n') { error("Unknown escape sequence. ", _line, position); } value = value.Substring(0, value.Length - 2).ToString() + "\n"; } }
advance(); } tokens.Add(new Token() { Type = TokenType.String, Value = value, Line = _line, Position = position - 1}); }
// match string literals if (match("'", null, TokenType.Integer, discard:true)) { int value; int position = _position; value = CurrentCharacter.ToCharArray()[0]; advance();
// deal with empty literals if (value == '\) error("Empty character literal", _line, _position);
// deal with escaped characters, only need to worry about \n and \\ // throw werror on any other if (value == '\\') { if (CurrentCharacter == "n") { value = '\n'; } else if (CurrentCharacter == "\\") { value = '\\'; } else { error("Unknown escape sequence. ", _line, _position - 1); } advance(); }
// if we haven't hit a closing ' here, there are two many characters // in the literal if (!match("'", null, TokenType.Integer, discard: true)) error("Multi-character constant", _line, _position);
tokens.Add(new Rosetta.Token() { Type = TokenType.Integer, Value = value.ToString(), Line = _line, Position = position - 1 }); }
// match comments by checking for starting token, then advancing // until closing token is matched if (match("/*", null, TokenType.None, exact: true, discard: true)) { while (!match("*/", null, TokenType.None, exact: true, discard: true)) { // reached the end of the file without closing comment! if (CurrentCharacter == "") error("End-of-file in comment. Closing comment characters not found.", _line, _position); advance(); } continue; }
// match complex operators match("<=", null, TokenType.Op_lessequal, exact: true); match(">=", null, TokenType.Op_greaterequal, exact: true); match("==", null, TokenType.Op_equal, exact: true); match("!=", null, TokenType.Op_notequal, exact: true); match("&&", null, TokenType.Op_and, exact: true); match("||", null, TokenType.Op_or, exact: true);
// match simple operators if (match(_operators, null, TokenType.None, maxLen:1)) { Token match = tokens.Last(); match.Type = _operatorTokenTypeMap[match.Value]; }
// brackets, braces and separators match("(", null, TokenType.LeftParen, exact: true); match(")", null, TokenType.RightParen, exact: true); match("{", null, TokenType.LeftBrace, exact: true); match("}", null, TokenType.RightBrace, exact: true); match(";", null, TokenType.Semicolon, exact: true); match(",", null, TokenType.Comma, exact: true);
}
// end of file token tokens.Add(new Rosetta.Token() { Type = TokenType.End_of_input, Line = _line, Position = _position }); return tokens; }
static void Main (string[] args) { StreamReader inputFile;
// if we passed in a filename, read code from that, else // read code from stdin if (args.Length > 0) { string path = args[0]; try { inputFile = new StreamReader(path); } catch (IOException) { inputFile = new StreamReader(Console.OpenStandardInput(8192)); } } else { inputFile = new StreamReader(Console.OpenStandardInput(8192)); }
string code = inputFile.ReadToEnd();
// strip windows line endings out code = code.Replace("\r", "");
LexicalScanner scanner = new LexicalScanner(code); List<Token> tokens = scanner.scan();
foreach(Token token in tokens) { Console.WriteLine(token.ToString()); } } }
} </lang>
- Output — test case 3:
5 16 Keyword_print 5 40 Op_subtract 6 16 Keyword_putc 6 40 Op_less 7 16 Keyword_if 7 40 Op_greater 8 16 Keyword_else 8 40 Op_lessequal 9 16 Keyword_while 9 40 Op_greaterequal 10 16 LeftBrace 10 40 Op_equal 11 16 RightBrace 11 40 Op_notequal 12 16 LeftParen 12 40 Op_and 13 16 RightParen 13 40 Op_or 14 16 Op_subtract 14 40 Semicolon 15 16 Op_not 15 40 Comma 16 16 Op_multiply 16 40 Op_assign 17 16 Op_divide 17 40 Integer 42 18 16 Op_mod 18 40 String "String literal" 19 16 Op_add 19 40 Identifier variable_name 20 26 Integer 10 21 26 Integer 92 22 26 Integer 32 23 1 End_of_input
Common Lisp
Lisp has a built-in reader and you can customize the reader by modifying its readtable. I'm also using the Gray stream, which is an almost standard feature of Common Lisp, for counting lines and columns.
<lang lisp>(defpackage #:lexical-analyzer
(:use #:cl #:sb-gray) (:export #:main))
(in-package #:lexical-analyzer)
(defclass counting-character-input-stream (fundamental-character-input-stream)
((stream :type stream :initarg :stream :reader stream-of) (line :type fixnum :initform 1 :accessor line-of) (column :type fixnum :initform 0 :accessor column-of) (prev-column :type (or null fixnum) :initform nil :accessor prev-column-of)) (:documentation "Character input stream that counts lines and columns."))
(defmethod stream-read-char ((stream counting-character-input-stream))
(let ((ch (read-char (stream-of stream) nil :eof))) (case ch (#\Newline (incf (line-of stream)) (setf (prev-column-of stream) (column-of stream) (column-of stream) 0)) (t (incf (column-of stream)))) ch))
(defmethod stream-unread-char ((stream counting-character-input-stream) char)
(unread-char char (stream-of stream)) (case char (#\Newline (decf (line-of stream)) (setf (column-of stream) (prev-column-of stream))) (t (decf (column-of stream)))))
(defstruct token
(name nil :type symbol) (value nil :type t) (line nil :type fixnum) (column nil :type fixnum))
(defun lexer-error (format-control &rest args)
(apply #'error format-control args))
(defun handle-divide-or-comment (stream char)
(declare (ignore char)) (case (peek-char nil stream t nil t) (#\* (loop with may-end = nil initially (read-char stream t nil t) for ch = (read-char stream t nil t) until (and may-end (char= ch #\/)) do (setf may-end (char= ch #\*)) finally (return (read stream t nil t)))) (t (make-token :name :op-divide :line (line-of stream) :column (column-of stream)))))
(defun make-constant-handler (token-name)
(lambda (stream char) (declare (ignore char)) (make-token :name token-name :line (line-of stream) :column (column-of stream))))
(defun make-this-or-that-handler (expect then &optional else)
(lambda (stream char) (declare (ignore char)) (let ((line (line-of stream)) (column (column-of stream)) (next (peek-char nil stream nil nil t))) (cond ((and expect (char= next expect)) (read-char stream nil nil t) (make-token :name then :line line :column column)) (else (make-token :name else :line line :column column)) (t (lexer-error "Unrecognized character '~A'" next))))))
(defun identifier? (symbol)
(and (symbolp symbol) (not (keywordp symbol)) (let ((name (symbol-name symbol))) (and (find (char name 0) "_abcdefghijklmnopqrstuvwxyz" :test #'char-equal) (or (< (length name) 2) (not (find-if-not (lambda (ch) (find ch "_abcdefghijklmnopqrstuvwxyz0123456789" :test #'char-equal)) name :start 1)))))))
(defun id->keyword (id line column)
(case id (|if| (make-token :name :keyword-if :line line :column column)) (|else| (make-token :name :keyword-else :line line :column column)) (|while| (make-token :name :keyword-while :line line :column column)) (|print| (make-token :name :keyword-print :line line :column column)) (|putc| (make-token :name :keyword-putc :line line :column column)) (t nil)))
(defun handle-identifier (stream char)
(let ((*readtable* (copy-readtable))) (set-syntax-from-char char #\z) (let ((line (line-of stream)) (column (column-of stream))) (unread-char char stream) (let ((obj (read stream t nil t))) (if (identifier? obj) (or (id->keyword obj line column) (make-token :name :identifier :value obj :line line :column column)) (lexer-error "Invalid identifier name: ~A" obj))))))
(defun handle-integer (stream char)
(let ((*readtable* (copy-readtable))) (set-syntax-from-char char #\z) (let ((line (line-of stream)) (column (column-of stream))) (unread-char char stream) (let ((obj (read stream t nil t))) (if (integerp obj) (make-token :name :integer :value obj :line line :column column) (lexer-error "Invalid integer: ~A" obj))))))
(defun handle-char-literal (stream char)
(declare (ignore char)) (let* ((line (line-of stream)) (column (column-of stream)) (ch (read-char stream t nil t)) (parsed (case ch (#\' (lexer-error "Empty character constant")) (#\Newline (lexer-error "New line in character literal")) (#\\ (let ((next-ch (read-char stream t nil t))) (case next-ch (#\n #\Newline) (#\\ #\\) (t (lexer-error "Unknown escape sequence: \\~A" next-ch))))) (t ch)))) (if (char= #\' (read-char stream t nil t)) (make-token :name :integer :value (char-code parsed) :line line :column column) (lexer-error "Only one character is allowed in character literal"))))
(defun handle-string (stream char)
(declare (ignore char)) (loop with result = (make-array 0 :element-type 'character :adjustable t :fill-pointer t) with line = (line-of stream) with column = (column-of stream) for ch = (read-char stream t nil t) until (char= ch #\") do (setf ch (case ch (#\Newline (lexer-error "New line in string")) (#\\ (let ((next-ch (read-char stream t nil t))) (case next-ch (#\n #\Newline) (#\\ #\\) (t (lexer-error "Unknown escape sequence: \\~A" next-ch))))) (t ch))) (vector-push-extend ch result) finally (return (make-token :name :string :value result :line line :column column))))
(defun make-lexer-readtable ()
(let ((*readtable* (copy-readtable nil))) (setf (readtable-case *readtable*) :preserve) (set-syntax-from-char #\\ #\z) (set-syntax-from-char #\# #\z) (set-syntax-from-char #\` #\z)
;; operators (set-macro-character #\* (make-constant-handler :op-multiply)) (set-macro-character #\/ #'handle-divide-or-comment) (set-macro-character #\% (make-constant-handler :op-mod)) (set-macro-character #\+ (make-constant-handler :op-add)) (set-macro-character #\- (make-constant-handler :op-subtract)) (set-macro-character #\< (make-this-or-that-handler #\= :op-lessequal :op-less)) (set-macro-character #\> (make-this-or-that-handler #\= :op-greaterequal :op-greater)) (set-macro-character #\= (make-this-or-that-handler #\= :op-equal :op-assign)) (set-macro-character #\! (make-this-or-that-handler #\= :op-notequal :op-not)) (set-macro-character #\& (make-this-or-that-handler #\& :op-and)) (set-macro-character #\| (make-this-or-that-handler #\| :op-or))
;; symbols (set-macro-character #\( (make-constant-handler :leftparen)) (set-macro-character #\) (make-constant-handler :rightparen)) (set-macro-character #\{ (make-constant-handler :leftbrace)) (set-macro-character #\} (make-constant-handler :rightbrace)) (set-macro-character #\; (make-constant-handler :semicolon)) (set-macro-character #\, (make-constant-handler :comma))
;; identifiers & keywords (set-macro-character #\_ #'handle-identifier t) (loop for ch across "abcdefghijklmnopqrstuvwxyz" do (set-macro-character ch #'handle-identifier t)) (loop for ch across "ABCDEFGHIJKLMNOPQRSTUVWXYZ" do (set-macro-character ch #'handle-identifier t))
;; integers (loop for ch across "0123456789" do (set-macro-character ch #'handle-integer t)) (set-macro-character #\' #'handle-char-literal)
;; strings (set-macro-character #\" #'handle-string)
*readtable*))
(defun lex-string (string)
(with-input-from-string (s string) (loop with *readtable* = (make-lexer-readtable) with eof = (gensym) with stream = (make-instance 'counting-character-input-stream :stream s) for token = (read stream nil eof) until (eq token eof) do (format t "~5D ~5D ~15A~@[ ~S~]~%" (token-line token) (token-column token) (token-name token) (token-value token)) finally (format t "~5D ~5D ~15A~%" (line-of stream) (column-of stream) :end-of-input) (close stream))))
(defun lex (file)
(with-open-file (s file) (let* ((buffer (make-array (file-length s) :element-type 'character :fill-pointer t)) (pos (read-sequence buffer s))) (setf (fill-pointer buffer) pos) (lex-string buffer))))
(defun main ()
(let ((file (uiop:command-line-arguments))) (if file (lex file) (error "File must be specified"))))</lang>
- Output — test case 3:
5 16 KEYWORD-PRINT 5 40 OP-SUBTRACT 6 16 KEYWORD-PUTC 6 40 OP-LESS 7 16 KEYWORD-IF 7 40 OP-GREATER 8 16 KEYWORD-ELSE 8 40 OP-LESSEQUAL 9 16 KEYWORD-WHILE 9 40 OP-GREATEREQUAL 10 16 LEFTBRACE 10 40 OP-EQUAL 11 16 RIGHTBRACE 11 40 OP-NOTEQUAL 12 16 LEFTPAREN 12 40 OP-AND 13 16 RIGHTPAREN 13 40 OP-OR 14 16 OP-SUBTRACT 14 40 SEMICOLON 15 16 OP-NOT 15 40 COMMA 16 16 OP-MULTIPLY 16 40 OP-ASSIGN 17 16 OP-DIVIDE 17 40 INTEGER 42 18 16 OP-MOD 18 40 STRING "String literal" 19 16 OP-ADD 19 40 IDENTIFIER variable_name 20 26 INTEGER 10 21 26 INTEGER 92 22 26 INTEGER 32 23 1 END-OF-INPUT
Euphoria
Tested with Euphoria 4.05. <lang euphoria>include std/io.e include std/map.e include std/types.e include std/convert.e
constant true = 1, false = 0, EOF = -1
enum tk_EOI, tk_Mul, tk_Div, tk_Mod, tk_Add, tk_Sub, tk_Negate, tk_Not, tk_Lss, tk_Leq,
tk_Gtr, tk_Geq, tk_Eq, tk_Neq, tk_Assign, tk_And, tk_Or, tk_If, tk_Else, tk_While, tk_Print, tk_Putc, tk_Lparen, tk_Rparen, tk_Lbrace, tk_Rbrace, tk_Semi, tk_Comma, tk_Ident, tk_Integer, tk_String
constant all_syms = {"End_of_input", "Op_multiply", "Op_divide", "Op_mod", "Op_add",
"Op_subtract", "Op_negate", "Op_not", "Op_less", "Op_lessequal", "Op_greater", "Op_greaterequal", "Op_equal", "Op_notequal", "Op_assign", "Op_and", "Op_or", "Keyword_if", "Keyword_else", "Keyword_while", "Keyword_print", "Keyword_putc", "LeftParen", "RightParen", "LeftBrace", "RightBrace", "Semicolon", "Comma", "Identifier", "Integer", "String"}
integer input_file, the_ch = ' ', the_col = 0, the_line = 1 sequence symbols map key_words = new()
procedure error(sequence format, sequence data)
printf(STDOUT, format, data) abort(1)
end procedure
-- get the next character from the input function next_ch()
the_ch = getc(input_file) the_col += 1 if the_ch = '\n' then the_line += 1 the_col = 0 end if return the_ch
end function
-- 'x' - character constants function char_lit(integer err_line, integer err_col)
integer n = next_ch() -- skip opening quote if the_ch = '\ then error("%d %d empty character constant", {err_line, err_col}) elsif the_ch = '\\' then next_ch() if the_ch = 'n' then n = 10 elsif the_ch = '\\' then n = '\\' else error("%d %d unknown escape sequence \\%c", {err_line, err_col, the_ch}) end if end if if next_ch() != '\ then error("%d %d multi-character constant", {err_line, err_col}) end if next_ch() return {tk_Integer, err_line, err_col, n}
end function
-- process divide or comments function div_or_cmt(integer err_line, integer err_col)
if next_ch() != '*' then return {tk_Div, err_line, err_col} end if
-- comment found next_ch() while true do if the_ch = '*' then if next_ch() = '/' then next_ch() return get_tok() end if elsif the_ch = EOF then error("%d %d EOF in comment", {err_line, err_col}) else next_ch() end if end while
end function
-- "string" function string_lit(integer start, integer err_line, integer err_col)
string text = ""
while next_ch() != start do if the_ch = EOF then error("%d %d EOF while scanning string literal", {err_line, err_col}) end if if the_ch = '\n' then error("%d %d EOL while scanning string literal", {err_line, err_col}) end if text &= the_ch end while
next_ch() return {tk_String, err_line, err_col, text}
end function
-- handle identifiers and integers function ident_or_int(integer err_line, integer err_col)
integer n, is_number = true string text = ""
while t_alnum(the_ch) or the_ch = '_' do text &= the_ch if not t_digit(the_ch) then is_number = false end if next_ch() end while
if length(text) = 0 then error("%d %d ident_or_int: unrecognized character: (%d) '%s'", {err_line, err_col, the_ch, the_ch}) end if
if t_digit(text[1]) then if not is_number then error("%d %d invalid number: %s", {err_line, err_col, text}) end if n = to_integer(text) return {tk_Integer, err_line, err_col, n} end if
if has(key_words, text) then return {get(key_words, text), err_line, err_col} end if
return {tk_Ident, err_line, err_col, text}
end function
-- look ahead for '>=', etc. function follow(integer expect, integer ifyes, integer ifno, integer err_line, integer err_col)
if next_ch() = expect then next_ch() return {ifyes, err_line, err_col} end if
if ifno = tk_EOI then error("%d %d follow: unrecognized character: (%d)", {err_line, err_col, the_ch}) end if
return {ifno, err_line, err_col}
end function
-- return the next token type function get_tok()
while t_space(the_ch) do next_ch() end while
integer err_line = the_line integer err_col = the_col
switch the_ch do case EOF then return {tk_EOI, err_line, err_col} case '/' then return div_or_cmt(err_line, err_col) case '\ then return char_lit(err_line, err_col)
case '<' then return follow('=', tk_Leq, tk_Lss, err_line, err_col) case '>' then return follow('=', tk_Geq, tk_Gtr, err_line, err_col) case '=' then return follow('=', tk_Eq, tk_Assign, err_line, err_col) case '!' then return follow('=', tk_Neq, tk_Not, err_line, err_col) case '&' then return follow('&', tk_And, tk_EOI, err_line, err_col) case '|' then return follow('|', tk_Or, tk_EOI, err_line, err_col)
case '"' then return string_lit(the_ch, err_line, err_col) case else integer sym = symbols[the_ch] if sym != tk_EOI then next_ch() return {sym, err_line, err_col} end if return ident_or_int(err_line, err_col) end switch
end function
procedure init()
put(key_words, "else", tk_Else) put(key_words, "if", tk_If) put(key_words, "print", tk_Print) put(key_words, "putc", tk_Putc) put(key_words, "while", tk_While)
symbols = repeat(tk_EOI, 256) symbols['{'] = tk_Lbrace symbols['}'] = tk_Rbrace symbols['('] = tk_Lparen symbols[')'] = tk_Rparen symbols['+'] = tk_Add symbols['-'] = tk_Sub symbols['*'] = tk_Mul symbols['%'] = tk_Mod symbols[';'] = tk_Semi symbols[','] = tk_Comma
end procedure
procedure main(sequence cl)
sequence file_name
input_file = STDIN if length(cl) > 2 then file_name = cl[3] input_file = open(file_name, "r") if input_file = -1 then error("Could not open %s", {file_name}) end if end if init() sequence t loop do t = get_tok() printf(STDOUT, "%5d %5d %-8s", {t[2], t[3], all_syms[t[1]]}) switch t[1] do case tk_Integer then printf(STDOUT, " %5d\n", {t[4]}) case tk_Ident then printf(STDOUT, " %s\n", {t[4]}) case tk_String then printf(STDOUT, " \"%s\"\n", {t[4]}) case else printf(STDOUT, "\n") end switch until t[1] = tk_EOI end loop
end procedure
main(command_line())</lang>
- Output — test case 3:
5 16 Keyword_print 5 40 Op_subtract 6 16 Keyword_putc 6 40 Op_less 7 16 Keyword_if 7 40 Op_greater 8 16 Keyword_else 8 40 Op_lessequal 9 16 Keyword_while 9 40 Op_greaterequal 10 16 LeftBrace 10 40 Op_equal 11 16 RightBrace 11 40 Op_notequal 12 16 LeftParen 12 40 Op_and 13 16 RightParen 13 40 Op_or 14 16 Op_subtract 14 40 Semicolon 15 16 Op_not 15 40 Comma 16 16 Op_multiply 16 40 Op_assign 17 16 Op_divide 17 40 Integer 42 18 16 Op_mod 18 40 String "String literal" 19 16 Op_add 19 40 Identifier variable_name 20 26 Integer 10 21 26 Integer 92 22 26 Integer 32 23 1 End_of_input
Flex
Tested with Flex 2.5.4. <lang C>%{
- include <stdio.h>
- include <stdlib.h>
- include <string.h>
- include <errno.h>
- include <limits.h>
- define NELEMS(arr) (sizeof(arr) / sizeof(arr[0]))
typedef enum {
tk_EOI, tk_Mul, tk_Div, tk_Mod, tk_Add, tk_Sub, tk_Negate, tk_Not, tk_Lss, tk_Leq, tk_Gtr, tk_Geq, tk_Eq, tk_Neq, tk_Assign, tk_And, tk_Or, tk_If, tk_Else, tk_While, tk_Print, tk_Putc, tk_Lparen, tk_Rparen, tk_Lbrace, tk_Rbrace, tk_Semi, tk_Comma, tk_Ident, tk_Integer, tk_String
} TokenType;
void yyerror(char msg[]) {
printf(msg); exit(1);
}
static int yynval;
struct yylloc {
int first_line, first_col; int last_line, last_col;
} yylloc;
static void update_loc() {
static int curr_line = 1; static int curr_col = 1;
yylloc.first_line = curr_line; yylloc.first_col = curr_col;
{char *s; for (s = yytext; *s != '\0'; s++) { if (*s == '\n') { curr_line++; curr_col = 1; } else { curr_col++; } }}
yylloc.last_line = curr_line; yylloc.last_col = curr_col-1;
}
- define YY_USER_ACTION update_loc();
static int kwd_cmp(const void *p1, const void *p2) {
return strcmp(*(char **)p1, *(char **)p2);
}
static TokenType get_ident_type(const char *ident) {
static struct { char *s; TokenType sym; } kwds[] = { {"else", tk_Else}, {"if", tk_If}, {"print", tk_Print}, {"putc", tk_Putc}, {"while", tk_While}, }, *kwp;
return (kwp = bsearch(&ident, kwds, NELEMS(kwds), sizeof(kwds[0]), kwd_cmp)) == NULL ? tk_Ident : kwp->sym;
}
%}
%start COMMENT2
%option noyywrap
digit [0-9] ident [a-zA-Z_][a-zA-Z_0-9]*
number {digit}+ string \"[^"\n]*\" char_const \'([^'\n]|\\n|\\\\)\'
%%
<COMMENT2>[^*]+ ; <COMMENT2>\*[^/] ; <COMMENT2>\*\/ BEGIN 0; /* end comment */ "/*" BEGIN COMMENT2;
"{" {return tk_Lbrace;} "}" {return tk_Rbrace;} "(" {return tk_Lparen;} ")" {return tk_Rparen;} "*" {return tk_Mul;} "/" {return tk_Div;} "%" {return tk_Mod;} "+" {return tk_Add;} "-" {return tk_Sub;} "<" {return tk_Lss;} ">" {return tk_Gtr;} "<=" {return tk_Leq;} ">=" {return tk_Geq;} "!=" {return tk_Neq;} "!" {return tk_Not;} "&&" {return tk_And;} "||" {return tk_Or;} ";" {return tk_Semi;} "," {return tk_Comma;} "==" {return tk_Eq;} "=" {return tk_Assign;} {ident} {return get_ident_type(yytext);} {string} {return tk_String;}
[ \t\n]+ ; /* ignore whitespace */
{number} {
yynval = strtol(yytext, NULL, 0); if (yynval == LONG_MAX && errno == ERANGE) yyerror("Number exceeds maximum value");
return tk_Integer; }
{char_const} {
int n = yytext[1]; char *p = yytext;
if (yyleng < 3) yyerror("empty character constant"); ++p; if (p[0] == '\\') { ++p; if (p[0] == 'n') n = 10; else if (p[0] == '\\') n = '\\'; else yyerror("unknown escape sequence"); } yynval = n; return tk_Integer; }
. yyerror("Unknown character\n");
%%
int main(int argc, char *argv[]) {
int tok;
++argv, --argc; /* skip over program name */ yyin = stdin; if (argc > 0) yyin = fopen(argv[0], "r");
do { tok = yylex(); printf("%5d %5d %.15s", yylloc.first_line, yylloc.first_col, &"End_of_input Op_multiply Op_divide Op_mod Op_add " "Op_subtract Op_negate Op_not Op_less Op_lessequal " "Op_greater Op_greaterequal Op_equal Op_notequal Op_assign " "Op_and Op_or Keyword_if Keyword_else Keyword_while " "Keyword_print Keyword_putc LeftParen RightParen LeftBrace " "RightBrace Semicolon Comma Identifier Integer " "String " [tok * 16]);
if (tok == tk_Integer) printf(" %5d", yynval); else if (tok == tk_Ident) printf(" %s", yytext); else if (tok == tk_String) printf(" %s", yytext); printf("\n"); } while (tok != tk_EOI); return 0;
}</lang>
- Output — test case 3:
5 16 Keyword_print 5 40 Op_subtract 6 16 Keyword_putc 6 40 Op_less 7 16 Keyword_if 7 40 Op_greater 8 16 Keyword_else 8 40 Op_lessequal 9 16 Keyword_while 9 40 Op_greaterequal 10 16 LeftBrace 10 40 Op_equal 11 16 RightBrace 11 40 Op_notequal 12 16 LeftParen 12 40 Op_and 13 16 RightParen 13 40 Op_or 14 16 Op_subtract 14 40 Semicolon 15 16 Op_not 15 40 Comma 16 16 Op_multiply 16 40 Op_assign 17 16 Op_divide 17 40 Integer 42 18 16 Op_mod 18 40 String "String literal" 19 16 Op_add 19 40 Identifier variable_name 20 26 Integer 10 21 26 Integer 92 22 26 Integer 32 22 29 End_of_input
FreeBASIC
Tested with FreeBASIC 1.05 <lang FreeBASIC>enum Token_type
tk_EOI tk_Mul tk_Div tk_Mod tk_Add tk_Sub tk_Negate tk_Not tk_Lss tk_Leq tk_Gtr tk_Geq tk_Eq tk_Neq tk_Assign tk_And tk_Or tk_If tk_Else tk_While tk_Print tk_Putc tk_Lparen tk_Rparen tk_Lbrace tk_Rbrace tk_Semi tk_Comma tk_Ident tk_Integer tk_String
end enum
const NewLine = chr(10) const DoubleQuote = chr(34) const BackSlash = chr(92)
' where we store keywords and variables type Symbol
s_name as string tok as Token_type
end type
dim shared symtab() as Symbol
dim shared cur_line as string dim shared cur_ch as string dim shared line_num as integer dim shared col_num as integer
function is_digit(byval ch as string) as long
is_digit = ch >= "0" AndAlso ch <= "9"
end function
function is_alnum(byval ch as string) as long
is_alnum = (ucase(ch) >= "A" AndAlso ucase(ch) <= "Z") OrElse is_digit(ch)
end function
sub error_msg(byval eline as integer, byval ecol as integer, byval msg as string)
print "("; eline; ":"; ecol; ") "; msg print : print "Hit any to end program" sleep system
end sub
' add an identifier to the symbol table function install(byval s_name as string, byval tok as Token_type) as integer
dim n as integer = ubound(symtab) + 1 redim preserve symtab(n)
symtab(n).s_name = s_name symtab(n).tok = tok return n
end function
' search for an identifier in the symbol table function lookup(byval s_name as string) as integer
dim i as integer
for i = lbound(symtab) to ubound(symtab) if symtab(i).s_name = s_name then return i next return -1
end function
sub next_line() ' read the next line of input from the source file
cur_line = "" cur_ch = "" ' empty cur_ch means end-of-file if eof(1) then exit sub line input #1, cur_line cur_line = cur_line + NewLine line_num += + 1 col_num = 1
end sub
sub next_char() ' get the next char
cur_ch = "" col_num += 1 if col_num > len(cur_line) then next_line() if col_num <= len(cur_line) then cur_ch = mid(cur_line, col_num, 1)
end sub
function follow(byval err_line as integer, byval err_col as integer, byval expect as string, byval ifyes as Token_type, byval ifno as Token_type) as Token_type
if cur_ch = expect then next_char() return ifyes end if if ifno = tk_eoi then error_msg(err_line, err_col, "follow unrecognized character: " + cur_ch) return ifno
end function
sub gettok(byref err_line as integer, byref err_col as integer, byref tok as Token_type, byref v as string)
' skip whitespace do while (cur_ch = " " or cur_ch = chr(9) or cur_ch = NewLine) and (cur_ch <> "") next_char() loop
err_line = line_num err_col = col_num
select case cur_ch case "": tok = tk_eoi: exit sub case "{": tok = tk_lbrace: next_char(): exit sub case "}": tok = tk_rbrace: next_char(): exit sub case "(": tok = tk_lparen: next_char(): exit sub case ")": tok = tk_rparen: next_char(): exit sub case "+": tok = tk_add: next_char(): exit sub case "-": tok = tk_sub: next_char(): exit sub case "*": tok = tk_mul: next_char(): exit sub case "%": tok = tk_Mod: next_char(): exit sub case ";": tok = tk_semi: next_char(): exit sub case ",": tok = tk_comma: next_char(): exit sub case "/": ' div or comment next_char() if cur_ch <> "*" then tok = tk_div exit sub end if ' skip comments next_char() do if cur_ch = "*" then next_char() if cur_ch = "/" then next_char() gettok(err_line, err_col, tok, v) exit sub end if elseif cur_ch = "" then error_msg(err_line, err_col, "EOF in comment") else next_char() end if loop case "'": ' single char literals next_char() v = str(asc(cur_ch)) if cur_ch = "'" then error_msg(err_line, err_col, "empty character constant") if cur_ch = BackSlash then next_char() if cur_ch = "n" then v = "10" elseif cur_ch = BackSlash then v = "92" else error_msg(err_line, err_col, "unknown escape sequence: " + cur_ch) end if end if next_char() if cur_ch <> "'" then error_msg(err_line, err_col, "multi-character constant") next_char() tok = tk_integer exit sub case "<": next_char(): tok = follow(err_line, err_col, "=", tk_Leq, tk_Lss): exit sub case ">": next_char(): tok = follow(err_line, err_col, "=", tk_Geq, tk_Gtr): exit sub case "!": next_char(): tok = follow(err_line, err_col, "=", tk_Neq, tk_Not): exit sub case "=": next_char(): tok = follow(err_line, err_col, "=", tk_Eq, tk_Assign): exit sub case "&": next_char(): tok = follow(err_line, err_col, "&", tk_And, tk_EOI): exit sub case "|": next_char(): tok = follow(err_line, err_col, "|", tk_Or, tk_EOI): exit sub case DoubleQuote: ' string v = cur_ch next_char() do while cur_ch <> DoubleQuote if cur_ch = NewLine then error_msg(err_line, err_col, "EOL in string") if cur_ch = "" then error_msg(err_line, err_col, "EOF in string") v += cur_ch next_char() loop v += cur_ch next_char() tok = tk_string exit sub case else ' integers or identifiers dim is_number as boolean = is_digit(cur_ch) v = "" do while is_alnum(cur_ch) orelse cur_ch = "_" if not is_digit(cur_ch) then is_number = false v += cur_ch next_char() loop if len(v) = 0 then error_msg(err_line, err_col, "unknown character: " + cur_ch) if is_digit(mid(v, 1, 1)) then if not is_number then error_msg(err_line, err_col, "invalid number: " + v) tok = tk_integer exit sub end if dim as integer index = lookup(v) if index = -1 then tok = tk_ident else tok = symtab(index).tok end if exit sub end select
end sub
sub init_lex(byval filein as string)
install("else", tk_else) install("if", tk_if) install("print", tk_print) install("putc", tk_putc) install("while", tk_while)
open filein for input as #1
cur_line = "" line_num = 0 col_num = 0 next_char()
end sub
sub scanner()
dim err_line as integer dim err_col as integer dim tok as Token_type dim v as string dim tok_list(tk_eoi to tk_string) as string
tok_list(tk_EOI ) = "End_of_input" tok_list(tk_Mul ) = "Op_multiply" tok_list(tk_Div ) = "Op_divide" tok_list(tk_Mod ) = "Op_mod" tok_list(tk_Add ) = "Op_add" tok_list(tk_Sub ) = "Op_subtract" tok_list(tk_Negate ) = "Op_negate" tok_list(tk_Not ) = "Op_not" tok_list(tk_Lss ) = "Op_less" tok_list(tk_Leq ) = "Op_lessequal" tok_list(tk_Gtr ) = "Op_greater" tok_list(tk_Geq ) = "Op_greaterequal" tok_list(tk_Eq ) = "Op_equal" tok_list(tk_Neq ) = "Op_notequal" tok_list(tk_Assign ) = "Op_assign" tok_list(tk_And ) = "Op_and" tok_list(tk_Or ) = "Op_or" tok_list(tk_If ) = "Keyword_if" tok_list(tk_Else ) = "Keyword_else" tok_list(tk_While ) = "Keyword_while" tok_list(tk_Print ) = "Keyword_print" tok_list(tk_Putc ) = "Keyword_putc" tok_list(tk_Lparen ) = "LeftParen" tok_list(tk_Rparen ) = "RightParen" tok_list(tk_Lbrace ) = "LeftBrace" tok_list(tk_Rbrace ) = "RightBrace" tok_list(tk_Semi ) = "Semicolon" tok_list(tk_Comma ) = "Comma" tok_list(tk_Ident ) = "Identifier" tok_list(tk_Integer) = "Integer" tok_list(tk_String ) = "String"
do gettok(err_line, err_col, tok, v) print using "##### ##### \ " + BackSlash; err_line; err_col; tok_list(tok); if tok = tk_integer orelse tok = tk_ident orelse tok = tk_string then print " " + v; print loop until tok = tk_eoi
end sub
sub main()
if command(1) = "" then print "filename required" : exit sub init_lex(command(1)) scanner()
end sub
main() print : print "Hit any to end program" sleep system</lang>
- Output — test case 3:
5 16 Keyword_print 5 40 Op_subtract 6 16 Keyword_putc 6 40 Op_less 7 16 Keyword_if 7 40 Op_greater 8 16 Keyword_else 8 40 Op_lessequal 9 16 Keyword_while 9 40 Op_greaterequal 10 16 LeftBrace 10 40 Op_equal 11 16 RightBrace 11 40 Op_notequal 12 16 LeftParen 12 40 Op_and 13 16 RightParen 13 40 Op_or 14 16 Op_subtract 14 40 Semicolon 15 16 Op_not 15 40 Comma 16 16 Op_multiply 16 40 Op_assign 17 16 Op_divide 17 40 Integer 42 18 16 Op_mod 18 40 String "String literal" 19 16 Op_add 19 40 Identifier variable_name 20 26 Integer 10 21 26 Integer 92 22 26 Integer 32 22 30 End_of_input
Perl
<lang perl>#!/usr/bin/env perl
use strict; use warnings; no warnings 'once';
- ----- Definition of the language to be lexed -----#
my @tokens = (
# Name | Format | Value # # -------------- |----------------------|-------------# ['Op_multiply' , '*' , ], ['Op_divide' , '/' , ], ['Op_mod' , '%' , ], ['Op_add' , '+' , ], ['Op_subtract' , '-' , ], ['Op_lessequal' , '<=' , ], ['Op_less' , '<' , ], ['Op_greaterequal', '>=' , ], ['Op_greater' , '>' , ], ['Op_equal' , '==' , ], ['Op_assign' , '=' , ], ['Op_not' , '!' , ], ['Op_notequal' , '!=' , ], ['Op_and' , '&&' , ], ['Op_or' , '||' , ], ['Keyword_else' , qr/else\b/ , ], ['Keyword_if' , qr/if\b/ , ], ['Keyword_while' , qr/while\b/ , ], ['Keyword_print' , qr/print\b/ , ], ['Keyword_putc' , qr/putc\b/ , ],
['LeftParen' , '(' , ], ['RightParen' , ')' , ], ['LeftBrace' , '{' , ], ['RightBrace' , '}' , ], ['Semicolon' , ';' , ], ['Comma' , ',' , ],
['Identifier' , qr/[_a-z][_a-z0-9]*/i, \&raw ], ['Integer' , qr/[0-9]+\b/ , \&raw ], ['Integer' , qr/'([^']*)(')?/ , \&char_val ], ['String' , qr/"([^"]*)(")?/ , \&string_raw],
['End_of_input' , qr/$/ , ],
);
my $comment = qr/\/\* .+? (?: \*\/ | $ (?{die "End-of-file in comment\n"}) )/xs; my $whitespace = qr/(?: \s | $comment)*/x; my $unrecognized = qr/\w+ | ./x;
- | Returns the value of a matched char literal, or dies if it is invalid
sub char_val {
my $str = string_val(); die "Multiple characters\n" if length $str > 1; die "No character\n" if length $str == 0; ord $str;
}
- | Returns the value of a matched string literal, or dies if it is invalid
sub string_val {
my ($str, $end) = ($1, $2); die "End-of-file\n" if not defined $end; die "End-of-line\n" if $str =~ /\n/; $str =~ s/\\(.)/ $1 eq 'n' ? "\n" : $1 eq '\\' ? $1 : $1 eq $end ? $1 : die "Unknown escape sequence \\$1\n" /rge;
}
- | Returns the source string of a matched literal
sub raw { $& }
- | Returns the source string of a matched string literal, or dies if invalid
sub string_raw {
string_val(); # Just for the error handling side-effects $&;
}
- ----- Lexer "engine" -----#
- Construct the scanner regex:
my $tokens =
join "|", map { my $format = $tokens[$_][1]; "\n".(ref $format ? $format : quotemeta $format)." (*MARK:$_) "; } 0..$#tokens;
my $regex = qr/
\G (?| $whitespace \K (?| $tokens ) | $whitespace? \K ($unrecognized) (*MARK:!) )
/x;
- Run the lexer:
my $input = do { local $/ = undef; <STDIN> }; my $pos = 0; my $linecol = linecol_accumulator();
while ($input =~ /$regex/g) {
# Get the line and column number my ($line, $col) = $linecol->(substr $input, $pos, $-[0] - $pos); $pos = $-[0];
# Get the token type that was identified by the scanner regex my $type = $main::REGMARK; die "Unrecognized token $1 at line $line, col $col\n" if $type eq '!'; my ($name, $evaluator) = @{$tokens[$type]}[0, 2];
# Get the token value my $value; if ($evaluator) { eval { $value = $evaluator->() }; if ($@) { chomp $@; die "$@ in $name at line $line, col $col\n" } }
# Print the output line print "$line\t$col\t$name".($value ? "\t$value" : )."\n";
}
- | Returns a closure, which can be fed a string one piece at a time and gives
- | back the cumulative line and column number each time
sub linecol_accumulator {
my ($line, $col) = (1, 1); sub { my $str = shift; my @lines = split "\n", $str, -1; my ($l, $c) = @lines ? (@lines - 1, length $lines[-1]) : (0, 0); if ($l) { $line += $l; $col = 1 + $c } else { $col += $c } ($line, $col) }
}</lang>
- Output — test case 3:
5 16 Keyword_print 5 40 Op_subtract 6 16 Keyword_putc 6 40 Op_less 7 16 Keyword_if 7 40 Op_greater 8 16 Keyword_else 8 40 Op_lessequal 9 16 Keyword_while 9 40 Op_greaterequal 10 16 LeftBrace 10 40 Op_equal 11 16 RightBrace 11 40 Op_not 11 41 Op_assign 12 16 LeftParen 12 40 Op_and 13 16 RightParen 13 40 Op_or 14 16 Op_subtract 14 40 Semicolon 15 16 Op_not 15 40 Comma 16 16 Op_multiply 16 40 Op_assign 17 16 Op_divide 17 40 Integer 42 18 16 Op_mod 18 40 String "String literal" 19 16 Op_add 19 40 Identifier variable_name 20 26 Integer 10 21 26 Integer 92 22 26 Integer 32 23 1 End_of_input
Perl 6
This is more complicated than strictly necessary for this task. It is set up to be easily adapted to do syntax analysis.
(Note: there are several bogus comments added solely to help with syntax highlighting.)
<lang perl6>grammar tiny_C {
rule TOP { ^ <.whitespace>? <tokens> + % <.whitespace> <.whitespace> <eoi> }
rule whitespace { [ <comment> + % <ws> | <ws> ] }
token comment { '/*' ~ '*/' .*? }
token tokens { [ | <operator> { make $/<operator>.ast } | <keyword> { make $/<keyword>.ast } | <symbol> { make $/<symbol>.ast } | <identifier> { make $/<identifier>.ast } | <integer> { make $/<integer>.ast } | <char> { make $/<char>.ast } | <string> { make $/<string>.ast } | <error> ] }
proto token operator {*} token operator:sym<*> { '*' { make 'Op_multiply' } } token operator:sym</> { '/'<!before '*'> { make 'Op_divide' } } token operator:sym<%> { '%' { make 'Op_mod' } } token operator:sym<+> { '+' { make 'Op_add' } } token operator:sym<-> { '-' { make 'Op_subtract' } } token operator:sym('<='){ '<=' { make 'Op_lessequal' } } token operator:sym('<') { '<' { make 'Op_less' } } token operator:sym('>='){ '>=' { make 'Op_greaterequal'} } token operator:sym('>') { '>' { make 'Op_greater' } } token operator:sym<==> { '==' { make 'Op_equal' } } token operator:sym<!=> { '!=' { make 'Op_notequal' } } token operator:sym<!> { '!' { make 'Op_not' } } token operator:sym<=> { '=' { make 'Op_assign' } } token operator:sym<&&> { '&&' { make 'Op_and' } } token operator:sym<||> { '||' { make 'Op_or' } }
proto token keyword {*} token keyword:sym<if> { 'if' { make 'Keyword_if' } } token keyword:sym<else> { 'else' { make 'Keyword_else' } } token keyword:sym<putc> { 'putc' { make 'Keyword_putc' } } token keyword:sym<while> { 'while' { make 'Keyword_while' } } token keyword:sym<print> { 'print' { make 'Keyword_print' } }
proto token symbol {*} token symbol:sym<(> { '(' { make 'LeftParen' } } token symbol:sym<)> { ')' { make 'RightParen' } } token symbol:sym<{> { '{' { make 'LeftBrace' } } token symbol:sym<}> { '}' { make 'RightBrace' } } token symbol:sym<;> { ';' { make 'Semicolon' } } token symbol:sym<,> { ',' { make 'Comma' } }
token identifier { <[_A..Za..z]><[_A..Za..z0..9]>* { make 'Identifier ' ~ $/ } } token integer { <[0..9]>+ { make 'Integer ' ~ $/ } }
token char { '\ [<-[']> | '\n' | '\\\\'] '\ { make 'Char_Literal ' ~ $/.subst("\\n", "\n").substr(1, *-1).ord } }
token string { '"' <-["\n]>* '"' #' { make 'String ' ~ $/; note 'Error: Unknown escape sequence.' and exit if (~$/ ~~ m:r/ <!after <[\\]>>[\\<-[n\\]>]<!before <[\\]>> /); } }
token eoi { $ { make 'End_of_input' } }
token error { | '\'\ { note 'Error: Empty character constant.' and exit } | '\ <-[']> ** {2..*} '\ { note 'Error: Multi-character constant.' and exit } | '/*' <-[*]>* $ { note 'Error: End-of-file in comment.' and exit } | '"' <-["]>* $ { note 'Error: End-of-file in string.' and exit } | '"' <-["]>*? \n { note 'Error: End of line in string.' and exit } #' }
}
sub parse_it ( $c_code ) {
my $l; my @pos = gather for $c_code.lines>>.chars.kv -> $line, $v { take [ $line + 1, $_ ] for 1 .. ($v+1); # v+1 for newline $l = $line+2; } @pos.push: [ $l, 1 ]; # capture eoi
for flat $c_code<tokens>.list, $c_code<eoi> -> $m { say join "\t", @pos[$m.from].fmt('%3d'), $m.ast; }
}
my $tokenizer = tiny_C.parse(@*ARGS[0].IO.slurp); parse_it( $tokenizer );</lang>
- Output — test case 3:
5 16 Keyword_print 5 40 Op_subtract 6 16 Keyword_putc 6 40 Op_less 7 16 Keyword_if 7 40 Op_greater 8 16 Keyword_else 8 40 Op_lessequal 9 16 Keyword_while 9 40 Op_greaterequal 10 16 LeftBrace 10 40 Op_equal 11 16 RightBrace 11 40 Op_notequal 12 16 LeftParen 12 40 Op_and 13 16 RightParen 13 40 Op_or 14 16 Op_subtract 14 40 Semicolon 15 16 Op_not 15 40 Comma 16 16 Op_multiply 16 40 Op_assign 17 16 Op_divide 17 40 Integer 42 18 16 Op_mod 18 40 String "String literal" 19 16 Op_add 19 40 Identifier variable_name 20 26 Char_Literal 10 21 26 Char_Literal 92 22 26 Char_Literal 32 23 1 End_of_input
Phix
Deviates from the task requirements in that it is written in a modular form so that the output from one stage can be used directly in the next, rather than re-loading from a human-readable form. If required, demo\rosetta\Compiler\extra.e contains some code that achieves the latter. Code to print the human readable forms is likewise kept separate from any re-usable parts.
<lang Phix>-- -- demo\\rosetta\\Compiler\\core.e -- =============================== -- -- Standard declarations and routines used by lex.exw, parse.exw, cgen.exw, and interp.exw -- (included in distribution as above, which contains some additional sanity checks) -- -- global constant EOF = -1, STDIN = 0, STDOUT = 1
global enum type nary NONE=0, UNARY=1, BINARY=2 end type
global sequence tkNames = {} -- eg/ie {"Op_multiply","Op_divide",..} global sequence precedences = {} global sequence narys = {} -- NONE/UNARY/BINARY global sequence operators = {} -- eg/ie {"*","/","+","-","<","<=",..} global sequence opcodes = {} -- idx to tkNames, matching operators
global constant KEYWORDS = new_dict() -- eg/ie {"if"=>idx to tkNames}
global enum OPERATOR=1, DIGIT, LETTER -- character classes
global sequence charmap = repeat(0,255)
charmap['0'..'9'] = DIGIT charmap['A'..'Z'] = LETTER charmap['a'..'z'] = LETTER charmap['_'] = LETTER
function tkName(string s, nary n = NONE, integer precedence = -1)
tkNames = append(tkNames,s) narys = append(narys,n) precedences = append(precedences,precedence) return length(tkNames)
end function
function tkOp(string s, string op, nary n, integer precedence)
integer res = tkName(s, n, precedence) operators = append(operators,op) opcodes = append(opcodes,res) for i=1 to length(op) do charmap[op[i]] = OPERATOR end for return res
end function
function tkKw(string s, string keyword)
integer res = tkName(s) putd(keyword, res, KEYWORDS) return res
end function
global constant
tk_EOI = tkName("End_of_input"), --1 tk_mul = tkOp("Op_multiply", "*", BINARY,13), --2 tk_div = tkOp("Op_divide", "/", BINARY,13), --3 tk_mod = tkOp("Op_mod", "%", BINARY,13), --4 tk_add = tkOp("Op_add", "+", BINARY,12), --5 tk_sub = tkOp("Op_subtract", "-", BINARY,12), --6 tk_neg = tkName("Op_negate", UNARY, 14), --7 tk_not = tkOp("Op_not", "!", UNARY, 14), --8 tk_lt = tkOp("Op_less", "<", BINARY,10), --9 tk_le = tkOp("Op_lessequal", "<=",BINARY,10), --10 tk_gt = tkOp("Op_greater", ">", BINARY,10), --11 tk_ge = tkOp("Op_greaterequal", ">=",BINARY,10), --12 tk_eq = tkOp("Op_equal", "==",BINARY, 9), --13 tk_ne = tkOp("Op_notequal", "!=",BINARY, 9), --14 tk_assign = tkOp("Op_assign", "=", NONE, -1), --15 tk_and = tkOp("Op_and", "&&",BINARY, 5), --16 tk_or = tkOp("Op_or", "||",BINARY, 4), --17 tk_if = tkKw("Keyword_if", "if"), --18 tk_else = tkKw("Keyword_else", "else"), --19 tk_while = tkKw("Keyword_while","while"), --20 tk_print = tkKw("Keyword_print","print"), --21 tk_putc = tkKw("Keyword_putc", "putc"), --22 tk_LeftParen = tkOp("LeftParen", "(", NONE, -1), --23 tk_RightParen = tkOp("RightParen", ")", NONE, -1), --24 tk_LeftBrace = tkOp("LeftBrace", "{", NONE, -1), --25 tk_RightBrace = tkOp("RightBrace", "}", NONE, -1), --26 tk_Semicolon = tkOp("Semicolon", ";", NONE, -1), --27 tk_Comma = tkOp("Comma", ",", NONE, -1), --28 tk_Identifier = tkName("Identifier"), --29 tk_Integer = tkName("Integer"), --30 tk_String = tkName("String"), --31 tk_Sequence = tkName("Sequence"), --32 tk_Prints = tkName("tk_Prints"), --33 tk_Printi = tkName("tk_Printi") --34
global integer input_file = STDIN,
output_file = STDOUT
type strint(object o)
return string(o) or integer(o)
end type
global strint tok_line, -- save of line/col at the start of
tok_col -- token/comment, for result/errors
global object oneline = ""
constant errfmt = "Line %s column %s:\n%s%s"
function errline()
oneline = substitute(trim(oneline,"\r\n"),"\t"," ") string padding = repeat(' ',tok_col) return sprintf("%s\n%s^ ",{oneline,padding})
end function
global procedure error(sequence msg, sequence args={})
if length(args) then msg = sprintf(msg,args) end if string el = iff(atom(oneline)?"":errline()) if integer(tok_line) then tok_line = sprintf("%d",tok_line) end if if integer(tok_col) then tok_col = sprintf("%d",tok_col) end if printf(STDOUT,errfmt,{tok_line,tok_col,el,msg}) {} = wait_key() abort(1)
end procedure
function open_file(string file_name, string mode)
integer fn = open(file_name, mode) if fn = -1 then printf(STDOUT, "Could not open %s", {file_name}) {} = wait_key() abort(1) end if return fn
end function
global procedure open_files(sequence cl)
if length(cl)>2 then input_file = open_file(cl[3],"r") if length(cl)>3 then output_file = open_file(cl[4],"w") end if end if
end procedure
global procedure close_files()
if input_file!=STDIN then close(input_file) end if if output_file!=STDOUT then close(output_file) end if
end procedure
global function enquote(string s)
return sprintf("\"%s\"",substitute(s,"\n","\\n"))
end function
global function unquote(string s)
if s[1]!='\"' then ?9/0 end if if s[$]!='\"' then ?9/0 end if s = substitute(s[2..-2],"\\n","\n") return s
end function</lang> The main lexer is also written to be reusable by later stages. <lang Phix>-- -- demo\\rosetta\\Compiler\\lex.e -- ============================== -- -- The reusable part of lex.exw -- This is only kept separate from core.e for consistency with later modules.
include core.e
integer ch = ' ',
line = 0, col = 0
procedure eof(string s)
error("%s in %s literal",{iff(ch=EOF?"EOF":"EOL"),s})
end procedure
function next_ch()
while 1 do col += 1 if oneline=EOF then ch = EOF exit elsif col>length(oneline) then line += 1 col = 0 oneline = gets(input_file) else ch = oneline[col] exit end if end while return ch
end function
constant whitespace = " \t\r\n\x0B\xA0" -- (0x0B is Vertical Tab, 0xA0 is Non-breaking space)
procedure skipspacesandcomments()
while 1 do if not find(ch,whitespace) then if ch='/' and col<length(oneline) and oneline[col+1]='*' then tok_line = line -- (in case of EOF error) tok_col = col ch = next_ch() -- (can be EOF) ch = next_ch() -- ( "" ) while 1 do if ch='*' then ch = next_ch() if ch='/' then exit end if elsif ch=EOF then error("EOF in comment") else ch = next_ch() end if end while else exit end if end if ch = next_ch() end while
end procedure
function escape_char(string s)
ch = next_ch() -- (discard the '\\') if ch='n' then ch = '\n' elsif ch='\\' then ch = '\\' elsif ch=EOF or ch='\n' then eof(s) else error("unknown escape sequence \\%c", {ch}) end if return ch
end function
function char_lit() integer startch = ch integer res = next_ch() -- (skip opening quote, save res)
if ch=startch then error("empty character constant") elsif ch='\\' then res = escape_char("character") end if ch = next_ch() if ch=EOF or ch='\n' then eof("character") elsif ch!=startch then error("multi-character constant") end if ch = next_ch() return {tk_Integer, res}
end function
function string_lit() integer startch = ch string text = ""
while next_ch()!=startch do if ch=EOF or ch='\n' then eof("string") elsif ch='\\' then ch = escape_char("string") end if text &= ch end while ch = next_ch() return {tk_String, text}
end function
function op() sequence operator = {ch}
ch = next_ch() while charmap[ch]=OPERATOR and find(operator&ch,operators) do -- (^ ie/eg merge ">=", but not ");") operator &= ch ch = next_ch() end while integer k = find(operator,operators) if k=0 then error("unknown operator") end if return {opcodes[k], 0} -- (0 unused)
end function
function int() integer i = 0
while charmap[ch]=DIGIT do i = i*10 + (ch-'0') ch = next_ch() end while if charmap[ch]=LETTER then error("invalid number") end if return {tk_Integer, i}
end function
function ident() string text = ""
while find(charmap[ch],{LETTER,DIGIT}) do text &= ch ch = next_ch() end while integer keyword = getd(text,KEYWORDS) if keyword!=NULL then return {keyword, 0} -- (0 unused) end if return {tk_Identifier, text}
end function
function get_tok()
skipspacesandcomments() tok_line = line tok_col = col switch ch do case EOF then return {tk_EOI, 0} -- (0 unused) case '\ then return char_lit() case '"' then return string_lit() else switch charmap[ch] do case OPERATOR then return op() case DIGIT then return int() case LETTER then return ident() else error("unrecognized character: (%d)", {ch}) end switch end switch
end function
global function lex() sequence toks = {}
integer tok = -1 object v while tok!=tk_EOI do {tok,v} = get_tok() toks = append(toks,{tok_line,tok_col,tok,v}) end while return toks
end function</lang> Finally, a simple test driver for the specific task: <lang Phix>-- -- demo\\rosetta\\Compiler\\lex.exw -- ================================ --
include lex.e
procedure main(sequence cl)
open_files(cl) sequence toks = lex() integer tok object v for i=1 to length(toks) do {tok_line,tok_col,tok,v} = toks[i] switch tok do case tk_Identifier: v = sprintf(" %s",v) case tk_Integer: v = sprintf(" %5d",v) case tk_String: v = sprintf(" %s",enquote(v)) else v = "" end switch printf(output_file, "%5d %5d %-10s%s\n", {tok_line,tok_col,tkNames[tok],v}) end for close_files()
end procedure
--main(command_line()) main({0,0,"test4.c"})</lang>
- Output:
2 1 Keyword_print 2 6 LeftParen 2 7 Integer 42 2 9 RightParen 2 10 Semicolon 3 1 Keyword_print 3 6 LeftParen 3 7 String "\nHello World\nGood Bye\nok\n" 3 38 RightParen 3 39 Semicolon 4 1 Keyword_print 4 6 LeftParen 4 7 String "Print a slash n - \n.\n" 4 33 RightParen 4 34 Semicolon 5 1 End_of_input
Python
Tested with Python 2.7 and 3.x <lang Python>from __future__ import print_function import sys
- following two must remain in the same order
tk_EOI, tk_Mul, tk_Div, tk_Mod, tk_Add, tk_Sub, tk_Negate, tk_Not, tk_Lss, tk_Leq, tk_Gtr, \ tk_Geq, tk_Eq, tk_Neq, tk_Assign, tk_And, tk_Or, tk_If, tk_Else, tk_While, tk_Print, \ tk_Putc, tk_Lparen, tk_Rparen, tk_Lbrace, tk_Rbrace, tk_Semi, tk_Comma, tk_Ident, \ tk_Integer, tk_String = range(31)
all_syms = ["End_of_input", "Op_multiply", "Op_divide", "Op_mod", "Op_add", "Op_subtract",
"Op_negate", "Op_not", "Op_less", "Op_lessequal", "Op_greater", "Op_greaterequal", "Op_equal", "Op_notequal", "Op_assign", "Op_and", "Op_or", "Keyword_if", "Keyword_else", "Keyword_while", "Keyword_print", "Keyword_putc", "LeftParen", "RightParen", "LeftBrace", "RightBrace", "Semicolon", "Comma", "Identifier", "Integer", "String"]
- single character only symbols
symbols = { '{': tk_Lbrace, '}': tk_Rbrace, '(': tk_Lparen, ')': tk_Rparen, '+': tk_Add, '-': tk_Sub,
'*': tk_Mul, '%': tk_Mod, ';': tk_Semi, ',': tk_Comma }
key_words = {'if': tk_If, 'else': tk_Else, 'print': tk_Print, 'putc': tk_Putc, 'while': tk_While}
the_ch = " " # dummy first char - but it must be a space the_col = 0 the_line = 1 input_file = None
- show error and exit
def error(line, col, msg):
print(line, col, msg) exit(1)
- get the next character from the input
def next_ch():
global the_ch, the_col, the_line
the_ch = input_file.read(1) the_col += 1 if the_ch == '\n': the_line += 1 the_col = 0 return the_ch
- 'x' - character constants
def char_lit(err_line, err_col):
n = ord(next_ch()) # skip opening quote if the_ch == '\: error(err_line, err_col, "empty character constant") elif the_ch == '\\': next_ch() if the_ch == 'n': n = 10 elif the_ch == '\\': n = ord('\\') else: error(err_line, err_col, "unknown escape sequence \\%c" % (the_ch)) if next_ch() != '\: error(err_line, err_col, "multi-character constant") next_ch() return tk_Integer, err_line, err_col, n
- process divide or comments
def div_or_cmt(err_line, err_col):
if next_ch() != '*': return tk_Div, err_line, err_col
# comment found next_ch() while True: if the_ch == '*': if next_ch() == '/': next_ch() return gettok() elif len(the_ch) == 0: error(err_line, err_col, "EOF in comment") else: next_ch()
- "string"
def string_lit(start, err_line, err_col):
text = ""
while next_ch() != start: if len(the_ch) == 0: error(err_line, err_col, "EOF while scanning string literal") if the_ch == '\n': error(err_line, err_col, "EOL while scanning string literal") text += the_ch
next_ch() return tk_String, err_line, err_col, text
- handle identifiers and integers
def ident_or_int(err_line, err_col):
is_number = True text = ""
while the_ch.isalnum() or the_ch == '_': text += the_ch if not the_ch.isdigit(): is_number = False next_ch()
if len(text) == 0: error(err_line, err_col, "ident_or_int: unrecognized character: (%d) '%c'" % (ord(the_ch), the_ch))
if text[0].isdigit(): if not is_number: error(err_line, err_col, "invalid number: %s" % (text)) n = int(text) return tk_Integer, err_line, err_col, n
if text in key_words: return key_words[text], err_line, err_col
return tk_Ident, err_line, err_col, text
- look ahead for '>=', etc.
def follow(expect, ifyes, ifno, err_line, err_col):
if next_ch() == expect: next_ch() return ifyes, err_line, err_col
if ifno == tk_EOI: error(err_line, err_col, "follow: unrecognized character: (%d) '%c'" % (ord(the_ch), the_ch))
return ifno, err_line, err_col
- return the next token type
def gettok():
while the_ch.isspace(): next_ch()
err_line = the_line err_col = the_col
if len(the_ch) == 0: return tk_EOI, err_line, err_col elif the_ch == '/': return div_or_cmt(err_line, err_col) elif the_ch == '\: return char_lit(err_line, err_col) elif the_ch == '<': return follow('=', tk_Leq, tk_Lss, err_line, err_col) elif the_ch == '>': return follow('=', tk_Geq, tk_Gtr, err_line, err_col) elif the_ch == '=': return follow('=', tk_Eq, tk_Assign, err_line, err_col) elif the_ch == '!': return follow('=', tk_Neq, tk_Not, err_line, err_col) elif the_ch == '&': return follow('&', tk_And, tk_EOI, err_line, err_col) elif the_ch == '|': return follow('|', tk_Or, tk_EOI, err_line, err_col) elif the_ch == '"': return string_lit(the_ch, err_line, err_col) elif the_ch in symbols: sym = symbols[the_ch] next_ch() return sym, err_line, err_col else: return ident_or_int(err_line, err_col)
- main driver
input_file = sys.stdin if len(sys.argv) > 1:
try: input_file = open(sys.argv[1], "r", 4096) except IOError as e: error(0, 0, "Can't open %s" % sys.argv[1])
while True:
t = gettok() tok = t[0] line = t[1] col = t[2]
print("%5d %5d %-14s" % (line, col, all_syms[tok]), end=)
if tok == tk_Integer: print(" %5d" % (t[3])) elif tok == tk_Ident: print(" %s" % (t[3])) elif tok == tk_String: print(' "%s"' % (t[3])) else: print("")
if tok == tk_EOI: break</lang>
- Output — test case 3:
5 16 Keyword_print 5 40 Op_subtract 6 16 Keyword_putc 6 40 Op_less 7 16 Keyword_if 7 40 Op_greater 8 16 Keyword_else 8 40 Op_lessequal 9 16 Keyword_while 9 40 Op_greaterequal 10 16 LeftBrace 10 40 Op_equal 11 16 RightBrace 11 40 Op_notequal 12 16 LeftParen 12 40 Op_and 13 16 RightParen 13 40 Op_or 14 16 Op_subtract 14 40 Semicolon 15 16 Op_not 15 40 Comma 16 16 Op_multiply 16 40 Op_assign 17 16 Op_divide 17 40 Integer 42 18 16 Op_mod 18 40 String "String literal" 19 16 Op_add 19 40 Identifier variable_name 20 26 Integer 10 21 26 Integer 92 22 26 Integer 32 23 1 End_of_input