Anonymous user
Parse EBNF: Difference between revisions
→{{header|PicoLisp}}
(Parse EBNF from string format) |
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factor : NUMBER ;</pre>
=={{header|Modula-2}}==
<lang Modula-2>
MODULE EBNF;
FROM ASCII IMPORT EOL;
FROM InOut IMPORT Done, Read, Write, WriteLn, WriteInt, WriteString;
FROM EBNFScanner IMPORT Symbol, sym, id, Ino, GetSym, MarkError, SkipLine;
FROM TableHandler IMPORT WordLength, Table, overflow, InitTable, Record, Tabulate;
VAR T0, T1 : Table;
PROCEDURE skip (n : INTEGER);
BEGIN
MarkError (n);
WHILE (sym < lpar) OR (sym > period) DO GetSym END
END skip;
PROCEDURE Expression;
PROCEDURE Term;
PROCEDURE Factor;
BEGIN
IF sym = ident THEN
Record (T0, id, Ino);
GetSym
ELSIF sym = literal THEN
Record (T1, id, Ino);
GetSym
ELSIF sym = lpar THEN
GetSym;
Expression;
IF sym = rpar THEN GetSym ELSE skip (2) END
ELSIF sym = lbk THEN
GetSym;
Expression;
IF sym = rbk THEN GetSym ELSE skip (3) END
ELSIF sym = lbr THEN
GetSym;
Expression;
IF sym = rbr THEN GetSym ELSE skip (4) END
ELSE
skip (5)
END
END Factor;
BEGIN
Factor;
WHILE sym < bar DO Factor END
END Term;
BEGIN
Term;
WHILE sym = bar DO
GetSym;
Term
END
END Expression;
PROCEDURE Production;
BEGIN
Record (T0, id, - INTEGER (Ino));
GetSym;
IF sym = eql THEN GetSym ELSE skip (7) END;
Expression;
IF sym # period THEN
MarkError (8);
SkipLine
END;
GetSym
END Production;
BEGIN
InitTable (T0);
InitTable (T1);
GetSym;
WHILE (sym = ident) AND (overflow = 0) DO Production END;
IF overflow > 0 THEN
WriteLn;
WriteString ("Table overflow");
WriteInt (overflow, 6);
END;
Write (35C);
Tabulate (T0);
Tabulate (T1);
END EBNF.</lang>
And the source for the EBNF scanner. I hope you like nested procedures.
<lang Modula-2>
IMPLEMENTATION MODULE EBNFScanner;
FROM ASCII IMPORT LF;
FROM InOut IMPORT Read, Write, WriteLn, WriteInt, WriteBf, EOF;
VAR ch : CHAR;
MODULE LineHandler;
IMPORT LF, EOF, ch, Ino, Read, Write, WriteLn, WriteInt, WriteBf;
EXPORT GetCh, MarkError, SkipLine;
CONST LineWidth = 100;
VAR cc : INTEGER;
cc1 : INTEGER;
cc2 : INTEGER;
line : ARRAY [0..LineWidth - 1] OF CHAR;
PROCEDURE GetLine;
BEGIN
IF cc2 > 0 THEN
WriteLn;
cc2 := 0
END;
Read (ch);
IF EOF () THEN
line [0] := 177C;
cc1 := 1
ELSE
INC (Ino);
WriteInt (Ino, 5);
Write (' ');
cc1 := 0;
LOOP
Write (ch);
line [cc1] := ch;
INC (cc1);
IF ch = LF THEN EXIT END;
Read (ch)
END
END
END GetLine;
PROCEDURE GetCh;
BEGIN
WHILE cc = cc1 DO
cc := 0;
GetLine
END;
ch := line [cc];
INC (cc)
END GetCh;
PROCEDURE MarkError (n : INTEGER);
BEGIN
IF cc2 = 0 THEN
Write ('*');
cc2 := 3;
REPEAT
Write (' ');
DEC (cc2)
UNTIL cc2 = 0;
END;
WHILE cc2 < cc DO
Write (' ');
INC (cc2)
END;
Write ('^');
WriteInt (n, 1);
INC (cc2, 2)
END MarkError;
PROCEDURE SkipLine;
BEGIN
WHILE ch # LF DO GetCh END;
GetCh
END SkipLine;
BEGIN (* BEGIN of LineHandler *)
cc := 0;
cc1 := 0;
cc2 := 0
END LineHandler;
PROCEDURE GetSym;
VAR i : CARDINAL;
BEGIN
WHILE ch <= ' ' DO GetCh END;
IF ch = '/' THEN
SkipLine;
WHILE ch <= ' ' DO GetCh END
END;
IF (CAP (ch) <= 'Z') AND (CAP (ch) >= 'A') THEN
i := 0;
sym := literal;
REPEAT
IF i < IdLength THEN
id [i] := ch;
INC (i)
END;
IF ch > 'Z' THEN sym := ident END;
GetCh
UNTIL (CAP (ch) < 'A') OR (CAP (ch) > 'Z');
id [i] := ' '
ELSIF ch = "'" THEN
i := 0;
GetCh;
sym := literal;
WHILE ch # "'" DO
IF i < IdLength THEN
id [i] := ch;
INC (i)
END;
GetCh
END;
GetCh;
id [i] := ' '
WHILE ch # "'" DO
IF i < IdLength THEN
id [i] := ch;
INC (i)
END;
GetCh
END;
GetCh;
id [i] := ' '
ELSIF ch = '"' THEN
i := 0;
GetCh;
sym := literal;
WHILE ch # '"' DO
IF i < IdLength THEN
id [i] := ch;
INC (i)
END;
GetCh
END;
GetCh;
id [i] := ' '
ELSIF ch = '=' THEN sym := eql; GetCh
ELSIF ch = '(' THEN sym := lpar; GetCh
ELSIF ch = ')' THEN sym := rpar; GetCh
ELSIF ch = '[' THEN sym := lbk; GetCh
ELSIF ch = ']' THEN sym := rbk; GetCh
ELSIF ch = '{' THEN sym := lbr; GetCh
ELSIF ch = '}' THEN sym := rbr; GetCh
ELSIF ch = '|' THEN sym := bar; GetCh
ELSIF ch = '.' THEN sym := period; GetCh
ELSIF ch = 177C THEN sym := other; GetCh
ELSE
sym := other;
GetCh
END
END GetSym;
BEGIN
Ino := 0;
ch := ' '
END EBNFScanner.</lang>
=={{header|PicoLisp}}==
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