Compiler/syntax analyzer: Difference between revisions

[https://en.wikipedia.org/wiki/Extended_Backus%E2%80%93Naur_Form Extended Backus-Naur Form (EBNF)]:

 

stmt_list = {stmt} ;

 

| '(' expr ')'

| ('+' | '-' | '!') primary

 

The resulting AST should be formulated as a Binary Tree.

|-

| style="vertical-align:top" |

while (count < 10) {

print("count is: ", count, "\n");

count = count + 1;

 

| style="vertical-align:top" |

[https://en.wikipedia.org/wiki/Recursive_descent_parser Recursive Descent] for statement parsing. The AST is also built:

 

if tok is "("

x = paren_expr()

t = make_node(Sequence, t, stmt())

until tok is end-of-file

 

;Once the AST is built, it should be output in a [[Flatten_a_list|flattened format.]] This can be as simple as the following:

 

if t == NULL

print(";\n")

print("\n")

prt_ast(t.left)

 

;If the AST is correctly built, loading it into a subsequent program should be as simple as:

 

line = readline()

# Each line has at least one token

left = load_ast()

right = load_ast()

 

Finally, the AST can also be tested by running it against one of the AST Interpreter [[Compiler/AST_interpreter|solutions]].

|-

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Simple prime number generator

*/

}

}

 

| style="vertical-align:top" |

 

=={{header|ALGOL W}}==

% parse tree nodes %

record node( integer type

while begin

if tkType = tString then begin

readToken

end

reference(node) listNode;

listNode := null;

listNode

end parseStatementList ;

 

tOp_multiply := 1; tkName( tOp_multiply ) := "Op_multiply"; tkPrec( tOp_multiply ) := 5;

tOp_divide := 2; tkName( tOp_divide ) := "Op_divide"; tkPrec( tOp_divide ) := 5;

tkNode( tOp_multiply ) := nMultiply; tkNode( tOp_divide ) := nDivide; tkNode( tOp_mod ) := nMod;

tkNode( tOp_add ) := nAdd; tkNode( tOp_subtract ) := nSubtract; tkNode( tOp_less ) := nLess;

tkNode( tOp_equal ) := nEqual; tkNode( tOp_notequal ) := nNotEqual; tkNode( tOp_not ) := nNot;

tkNode( tOp_and ) := nAnd; tkNode( tOp_or ) := nOr;

readToken;

writeNode( parseStatementList( tEnd_of_input ) )

{{out}}

Output from parsing the Prime Numbers example program.

;

</pre>

 

=={{header|AWK}}==

Tested with gawk 4.1.1 and mawk 1.3.4.

function Token_assign(tk, attr, attr_array, n, i) {

n=split(attr, attr_array)

prt_ast(t)

}

 

{{out|case=count}}

=={{header|C}}==

Tested with gcc 4.81 and later, compiles warning free with -Wall -Wextra

#include <stdlib.h>

#include <string.h>

init_io(&dest_fp, stdout, "wb", argc > 2 ? argv[2] : "");

prt_ast(parse());

 

{{out|case=prime numbers AST}}

Code by Steve Williams. Tested with GnuCOBOL 2.2.

 

identification division.

*> this code is dedicated to the public domain

.

end program printast.

 

{{out|case=Primes}}

String "\n"

;</pre>

 

=={{header|Forth}}==

Tested with Gforth 0.7.3.

: PEEK BUF @ 0= IF KEY BUF ! THEN BUF @ ;

: GETC PEEK 0 BUF ! ;

: -EOI? TOKEN-TYPE End_of_input <> ;

: PARSE $NULL GETTOK BEGIN -EOI? WHILE STMT $SEQUENCE REPEAT ;

 

{{out|case=Count AST}}

</b>

 

 

=={{header|Go}}==

{{trans|C}}

 

import (

scanner = bufio.NewScanner(source)

prtAst(parse())

 

{{out}}

;

</pre>