File size: 10,227 Bytes
3dcad1f |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 |
;;;; string-peg.scm --- representing PEG grammars as strings
;;;;
;;;; Copyright (C) 2010, 2011 Free Software Foundation, Inc.
;;;;
;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public
;;;; License as published by the Free Software Foundation; either
;;;; version 3 of the License, or (at your option) any later version.
;;;;
;;;; This library is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;;;; Lesser General Public License for more details.
;;;;
;;;; You should have received a copy of the GNU Lesser General Public
;;;; License along with this library; if not, write to the Free Software
;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
;;;;
(define-module (ice-9 peg string-peg)
#:export (peg-as-peg
define-peg-string-patterns
peg-grammar)
#:use-module (ice-9 peg using-parsers)
#:use-module (ice-9 peg codegen)
#:use-module (ice-9 peg simplify-tree))
;; Gets the left-hand depth of a list.
(define (depth lst)
(if (or (not (list? lst)) (null? lst))
0
(+ 1 (depth (car lst)))))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;; Parse string PEGs using sexp PEGs.
;; See the variable PEG-AS-PEG for an easier-to-read syntax.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Grammar for PEGs in PEG grammar.
(define peg-as-peg
"grammar <-- (nonterminal ('<--' / '<-' / '<') sp pattern)+
pattern <-- alternative (SLASH sp alternative)*
alternative <-- ([!&]? sp suffix)+
suffix <-- primary ([*+?] sp)*
primary <-- '(' sp pattern ')' sp / '.' sp / literal / charclass / nonterminal !'<'
literal <-- ['] (!['] .)* ['] sp
charclass <-- LB (!']' (CCrange / CCsingle))* RB sp
CCrange <-- . '-' .
CCsingle <-- .
nonterminal <-- [a-zA-Z0-9-]+ sp
sp < [ \t\n]*
SLASH < '/'
LB < '['
RB < ']'
")
(define-syntax define-sexp-parser
(lambda (x)
(syntax-case x ()
((_ sym accum pat)
(let* ((matchf (compile-peg-pattern #'pat (syntax->datum #'accum)))
(accumsym (syntax->datum #'accum))
(syn (wrap-parser-for-users x matchf accumsym #'sym)))
#`(define sym #,syn))))))
(define-sexp-parser peg-grammar all
(+ (and peg-nonterminal (or "<--" "<-" "<") peg-sp peg-pattern)))
(define-sexp-parser peg-pattern all
(and peg-alternative
(* (and (ignore "/") peg-sp peg-alternative))))
(define-sexp-parser peg-alternative all
(+ (and (? (or "!" "&")) peg-sp peg-suffix)))
(define-sexp-parser peg-suffix all
(and peg-primary (* (and (or "*" "+" "?") peg-sp))))
(define-sexp-parser peg-primary all
(or (and "(" peg-sp peg-pattern ")" peg-sp)
(and "." peg-sp)
peg-literal
peg-charclass
(and peg-nonterminal (not-followed-by "<"))))
(define-sexp-parser peg-literal all
(and "'" (* (and (not-followed-by "'") peg-any)) "'" peg-sp))
(define-sexp-parser peg-charclass all
(and (ignore "[")
(* (and (not-followed-by "]")
(or charclass-range charclass-single)))
(ignore "]")
peg-sp))
(define-sexp-parser charclass-range all (and peg-any "-" peg-any))
(define-sexp-parser charclass-single all peg-any)
(define-sexp-parser peg-nonterminal all
(and (+ (or (range #\a #\z) (range #\A #\Z) (range #\0 #\9) "-")) peg-sp))
(define-sexp-parser peg-sp none
(* (or " " "\t" "\n")))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;; PARSE STRING PEGS
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Takes a string representing a PEG grammar and returns syntax that
;; will define all of the nonterminals in the grammar with equivalent
;; PEG s-expressions.
(define (peg-parser str for-syntax)
(let ((parsed (match-pattern peg-grammar str)))
(if (not parsed)
(begin
;; (display "Invalid PEG grammar!\n")
#f)
(let ((lst (peg:tree parsed)))
(cond
((or (not (list? lst)) (null? lst))
lst)
((eq? (car lst) 'peg-grammar)
#`(begin
#,@(map (lambda (x) (peg-nonterm->defn x for-syntax))
(context-flatten (lambda (lst) (<= (depth lst) 2))
(cdr lst))))))))))
;; Macro wrapper for PEG-PARSER. Parses PEG grammars expressed as strings and
;; defines all the appropriate nonterminals.
(define-syntax define-peg-string-patterns
(lambda (x)
(syntax-case x ()
((_ str)
(peg-parser (syntax->datum #'str) x)))))
;; lst has format (nonterm grabber pattern), where
;; nonterm is a symbol (the name of the nonterminal),
;; grabber is a string (either "<", "<-" or "<--"), and
;; pattern is the parse of a PEG pattern expressed as as string.
(define (peg-nonterm->defn lst for-syntax)
(let* ((nonterm (car lst))
(grabber (cadr lst))
(pattern (caddr lst))
(nonterm-name (datum->syntax for-syntax
(string->symbol (cadr nonterm)))))
#`(define-peg-pattern #,nonterm-name
#,(cond
((string=? grabber "<--") (datum->syntax for-syntax 'all))
((string=? grabber "<-") (datum->syntax for-syntax 'body))
(else (datum->syntax for-syntax 'none)))
#,(compressor (peg-pattern->defn pattern for-syntax) for-syntax))))
;; lst has format ('peg-pattern ...).
;; After the context-flatten, (cdr lst) has format
;; (('peg-alternative ...) ...), where the outer list is a collection
;; of elements from a '/' alternative.
(define (peg-pattern->defn lst for-syntax)
#`(or #,@(map (lambda (x) (peg-alternative->defn x for-syntax))
(context-flatten (lambda (x) (eq? (car x) 'peg-alternative))
(cdr lst)))))
;; lst has format ('peg-alternative ...).
;; After the context-flatten, (cdr lst) has the format
;; (item ...), where each item has format either ("!" ...), ("&" ...),
;; or ('peg-suffix ...).
(define (peg-alternative->defn lst for-syntax)
#`(and #,@(map (lambda (x) (peg-body->defn x for-syntax))
(context-flatten (lambda (x) (or (string? (car x))
(eq? (car x) 'peg-suffix)))
(cdr lst)))))
;; lst has the format either
;; ("!" ('peg-suffix ...)), ("&" ('peg-suffix ...)), or
;; ('peg-suffix ...).
(define (peg-body->defn lst for-syntax)
(cond
((equal? (car lst) "&")
#`(followed-by #,(peg-suffix->defn (cadr lst) for-syntax)))
((equal? (car lst) "!")
#`(not-followed-by #,(peg-suffix->defn (cadr lst) for-syntax)))
((eq? (car lst) 'peg-suffix)
(peg-suffix->defn lst for-syntax))
(else `(peg-parse-body-fail ,lst))))
;; lst has format ('peg-suffix <peg-primary> (? (/ "*" "?" "+")))
(define (peg-suffix->defn lst for-syntax)
(let ((inner-defn (peg-primary->defn (cadr lst) for-syntax)))
(cond
((null? (cddr lst))
inner-defn)
((equal? (caddr lst) "*")
#`(* #,inner-defn))
((equal? (caddr lst) "?")
#`(? #,inner-defn))
((equal? (caddr lst) "+")
#`(+ #,inner-defn)))))
;; Parse a primary.
(define (peg-primary->defn lst for-syntax)
(let ((el (cadr lst)))
(cond
((list? el)
(cond
((eq? (car el) 'peg-literal)
(peg-literal->defn el for-syntax))
((eq? (car el) 'peg-charclass)
(peg-charclass->defn el for-syntax))
((eq? (car el) 'peg-nonterminal)
(datum->syntax for-syntax (string->symbol (cadr el))))))
((string? el)
(cond
((equal? el "(")
(peg-pattern->defn (caddr lst) for-syntax))
((equal? el ".")
(datum->syntax for-syntax 'peg-any))
(else (datum->syntax for-syntax
`(peg-parse-any unknown-string ,lst)))))
(else (datum->syntax for-syntax
`(peg-parse-any unknown-el ,lst))))))
;; Trims characters off the front and end of STR.
;; (trim-1chars "'ab'") -> "ab"
(define (trim-1chars str) (substring str 1 (- (string-length str) 1)))
;; Parses a literal.
(define (peg-literal->defn lst for-syntax)
(datum->syntax for-syntax (trim-1chars (cadr lst))))
;; Parses a charclass.
(define (peg-charclass->defn lst for-syntax)
#`(or
#,@(map
(lambda (cc)
(cond
((eq? (car cc) 'charclass-range)
#`(range #,(datum->syntax
for-syntax
(string-ref (cadr cc) 0))
#,(datum->syntax
for-syntax
(string-ref (cadr cc) 2))))
((eq? (car cc) 'charclass-single)
(datum->syntax for-syntax (cadr cc)))))
(context-flatten
(lambda (x) (or (eq? (car x) 'charclass-range)
(eq? (car x) 'charclass-single)))
(cdr lst)))))
;; Compresses a list to save the optimizer work.
;; e.g. (or (and a)) -> a
(define (compressor-core lst)
(if (or (not (list? lst)) (null? lst))
lst
(cond
((and (or (eq? (car lst) 'or) (eq? (car lst) 'and))
(null? (cddr lst)))
(compressor-core (cadr lst)))
((and (eq? (car lst) 'body)
(eq? (cadr lst) 'lit)
(eq? (cadddr lst) 1))
(compressor-core (caddr lst)))
(else (map compressor-core lst)))))
(define (compressor syn for-syntax)
(datum->syntax for-syntax
(compressor-core (syntax->datum syn))))
;; Builds a lambda-expressions for the pattern STR using accum.
(define (peg-string-compile args accum)
(syntax-case args ()
((str-stx) (string? (syntax->datum #'str-stx))
(let ((string (syntax->datum #'str-stx)))
(compile-peg-pattern
(compressor
(peg-pattern->defn
(peg:tree (match-pattern peg-pattern string)) #'str-stx)
#'str-stx)
(if (eq? accum 'all) 'body accum))))
(else (error "Bad embedded PEG string" args))))
(add-peg-compiler! 'peg peg-string-compile)
|