/peg/peg.peg

http://github.com/feyeleanor/RubyGoLightly · Unknown · 77 lines · 71 code · 6 blank · 0 comment · 0 complexity · 67dac4fef4ce3b75dfc5df2b05cd9370 MD5 · raw file 

    

  1. # PE Grammar for PE Grammars
    2. 

  2. # 
    3. 

  3. # Adapted from [1] by Ian Piumarta <first-name at last-name point com>.
    4. 

  4. # 
    5. 

  5. # Local modifications (marked '#ikp') to support:
    6. 

  6. #     C text in '{ ... }' copied verbatim to output as 'semantic action'
    7. 

  7. #     input consumed between '<' and '>' is 'char yytext[]' in semantic actions
    8. 

  8. # 
    9. 

  9. # Best viewed using 140 columns monospaced with tabs every 8.
    10. 

  10. # 
    11. 

  11. # [1] Bryan Ford.  "Parsing Expression Grammars: A Recognition-Based Syntactic
    12. 

  12. #     Foundation."  Symposium on Principles of Programming Languages,
    13. 

  13. #     January 14--16, 2004, Venice, Italy.
    14. 

  14. # 
    15. 

  15. # Last edited: 2007-05-15 10:32:44 by piumarta on emilia
    16. 

  16. 

  17. # Hierarchical syntax
    18. 

  18. 

  19. Grammar		<- Spacing Definition+ EndOfFile
    20. 

  20. 

  21. Definition	<- Identifier 			{ if (push(beginRule(findRule(yytext)))->rule.expression) fprintf(stderr, "rule '%s' redefined\n", yytext); }
    22. 

  22. 		     LEFTARROW Expression	{ Node *e= pop();  Rule_setExpression(pop(), e); } &{ YYACCEPT }
    23. 

  23. Expression	<- Sequence (SLASH Sequence	{ Node *f= pop();  push(Alternate_append(pop(), f)); }
    24. 

  24. 			    )*
    25. 

  25. Sequence	<- Prefix (Prefix		{ Node *f= pop();  push(Sequence_append(pop(), f)); }	#ikp expanded from 'Seq <- Prefix*'
    26. 

  26. 			  )*
    27. 

  27. 		 / 				{ push(Predicate{text: "1"}); }				#ikp added
    28. 

  28. Prefix		<- AND Action			{ push(Predicate{text: yytext}); }	#ikp added
    29. 

  29. 		 / AND Suffix			{ push(PeekFor{element: pop()}); }		#ikp expanded from 'Prefix <- (AND/NOT)? Suffix'
    30. 

  30. 		 / NOT Suffix			{ push(PeekNot{element: pop()}); }
    31. 

  31. 		 /     Suffix
    32. 

  32. Suffix		<- Primary (QUESTION		{ push(Query{element: pop()}); }
    33. 

  33. 			     / STAR		{ push(Star{element: pop()}); }
    34. 

  34. 			     / PLUS		{ push(Plus{element: pop()}); }
    35. 

  35. 			   )?
    36. 

  36. Primary		<- Identifier !LEFTARROW	{ push(Name{used: true, variable: nil, rule: findRule(yytext)}); }
    37. 

  37. 		 / OPEN Expression CLOSE
    38. 

  38. 		 / Literal			{ push(String{value: yytext}); }
    39. 

  39. 		 / Class			{ push(Class{cclass: yytext}); }
    40. 

  40. 		 / DOT				{ push(Dot{}); }
    41. 

  41. 		 / Action			{ push(makeAction(yytext)); }		#ikp added
    42. 

  42. 		 / BEGIN			{ push(Predicate{text: "YY_BEGIN"}); }	#ikp added
    43. 

  43. 		 / END				{ push(Predicate{text: "YY_END"}); }	#ikp added
    44. 

  44. 

  45. # Lexical syntax
    46. 

  46. 

  47. Identifier	<- < IdentStart IdentCont* > Spacing		#ikp inserted < ... >
    48. 

  48. IdentStart	<- [a-zA-Z_]
    49. 

  49. IdentCont	<- IdentStart / [0-9]
    50. 

  50. Literal		<- ['] < (!['] Char )* > ['] Spacing		#ikp inserted < ... >
    51. 

  51. 		 / ["] < (!["] Char )* > ["] Spacing		#ikp inserted < ... >
    52. 

  52. Class		<- '[' < (!']' Range)* > ']' Spacing		#ikp inserted < ... >
    53. 

  53. Range		<- Char '-' Char / Char
    54. 

  54. Char		<- '\\' [abefnrtv'"\[\]\\]			#ikp added missing ANSI escapes: abefv
    55. 

  55. 		 / '\\' [0-3][0-7][0-7]
    56. 

  56. 		 / '\\' [0-7][0-7]?
    57. 

  57. 		 / '\\' '-'					#ikp added
    58. 

  58. 		 / !'\\' .
    59. 

  59. LEFTARROW	<- '<-' Spacing
    60. 

  60. SLASH		<- '/' Spacing
    61. 

  61. AND		<- '&' Spacing
    62. 

  62. NOT		<- '!' Spacing
    63. 

  63. QUESTION	<- '?' Spacing
    64. 

  64. STAR		<- '*' Spacing
    65. 

  65. PLUS		<- '+' Spacing
    66. 

  66. OPEN		<- '(' Spacing
    67. 

  67. CLOSE		<- ')' Spacing
    68. 

  68. DOT		<- '.' Spacing
    69. 

  69. Spacing		<- (Space / Comment)*
    70. 

  70. Comment		<- '#' (!EndOfLine .)* EndOfLine
    71. 

  71. Space		<- ' ' / '\t' / EndOfLine
    72. 

  72. EndOfLine	<- '\r\n' / '\n' / '\r'
    73. 

  73. EndOfFile	<- !.
    74. 

  74. 

  75. Action		<- '{' < [^}]* > '}' Spacing		#ikp added
    76. 

  76. BEGIN		<- '<' Spacing				#ikp added
    77. 

  77. END		<- '>' Spacing				#ikp added
    78.