# PE Grammar for PE Grammars
# 
# Adapted from [1] by Ian Piumarta <first-name at last-name point com>.
# 
# Local modifications (marked '#ikp') to support:
#     C text in '{ ... }' copied verbatim to output as 'semantic action'
#     input consumed between '<' and '>' is 'char yytext[]' in semantic actions
# 
# Best viewed using 140 columns monospaced with tabs every 8.
# 
# [1] Bryan Ford.  "Parsing Expression Grammars: A Recognition-Based Syntactic
#     Foundation."  Symposium on Principles of Programming Languages,
#     January 14--16, 2004, Venice, Italy.
# 
# Last edited: 2007-05-15 10:32:44 by piumarta on emilia
 
# Hierarchical syntax
 
Grammar    <- Spacing Definition+ EndOfFile
 
Definition  <- Identifier       { if (push(beginRule(findRule(yytext)))->rule.expression) fprintf(stderr, "rule '%s' redefined\n", yytext); }
         LEFTARROW Expression  { Node *e= pop();  Rule_setExpression(pop(), e); } &{ YYACCEPT }
Expression  <- Sequence (SLASH Sequence  { Node *f= pop();  push(Alternate_append(pop(), f)); }
          )*
Sequence  <- Prefix (Prefix    { Node *f= pop();  push(Sequence_append(pop(), f)); }  #ikp expanded from 'Seq <- Prefix*'
        )*
     /         { push(makePredicate("1")); }        #ikp added
Prefix    <- AND Action      { push(makePredicate(yytext)); }  #ikp added
     / AND Suffix      { push(makePeekFor(pop())); }    #ikp expanded from 'Prefix <- (AND/NOT)? Suffix'
     / NOT Suffix      { push(makePeekNot(pop())); }
     /     Suffix
Suffix    <- Primary (QUESTION    { push(makeQuery(pop())); }
           / STAR    { push(makeStar (pop())); }
           / PLUS    { push(makePlus (pop())); }
         )?
Primary    <- Identifier !LEFTARROW  { push(makeName(findRule(yytext))); }
     / OPEN Expression CLOSE
     / Literal      { push(makeString(yytext)); }
     / Class      { push(makeClass(yytext)); }
     / DOT        { push(makeDot()); }
     / Action      { push(makeAction(yytext)); }    #ikp added
     / BEGIN      { push(makePredicate("YY_BEGIN")); }  #ikp added
     / END        { push(makePredicate("YY_END")); }  #ikp added
 
# Lexical syntax
 
Identifier  <- < IdentStart IdentCont* > Spacing    #ikp inserted < ... >
IdentStart  <- [a-zA-Z_]
IdentCont  <- IdentStart / [0-9]
Literal    <- ['] < (!['] Char )* > ['] Spacing    #ikp inserted < ... >
     / ["] < (!["] Char )* > ["] Spacing    #ikp inserted < ... >
Class    <- '[' < (!']' Range)* > ']' Spacing    #ikp inserted < ... >
Range    <- Char '-' Char / Char
Char    <- '\\' [abefnrtv'"\[\]\\]      #ikp added missing ANSI escapes: abefv
     / '\\' [0-3][0-7][0-7]
     / '\\' [0-7][0-7]?
     / '\\' '-'          #ikp added
     / !'\\' .
LEFTARROW  <- '<-' Spacing
SLASH    <- '/' Spacing
AND    <- '&' Spacing
NOT    <- '!' Spacing
QUESTION  <- '?' Spacing
STAR    <- '*' Spacing
PLUS    <- '+' Spacing
OPEN    <- '(' Spacing
CLOSE    <- ')' Spacing
DOT    <- '.' Spacing
Spacing    <- (Space / Comment)*
Comment    <- '#' (!EndOfLine .)* EndOfLine
Space    <- ' ' / '\t' / EndOfLine
EndOfLine  <- '\r\n' / '\n' / '\r'
EndOfFile  <- !.
 
Action    <- '{' < [^}]* > '}' Spacing    #ikp added
BEGIN    <- '<' Spacing        #ikp added
END    <- '>' Spacing        #ikp added