/usr/share/racket/collects/syntax/template.rkt is in racket-common 6.7-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 | #lang racket/base
(require "stx.rkt"
racket/struct
(for-template racket/base
"private/template-runtime.rkt"))
(provide transform-template)
;; A template map descibres the structure of a template
;; in terms of where pattern variables are replaced.
;;
;; Walk a map and a template in parallel, and you see
;; these map cases:
;;
;; - #f => corresponding template portion is constant
;; - #t => corresponding template portion is a pattern variable
;; - (cons map1 map2) => template part is a pair
;; which substitutions in one side
;; or the other
;; - (vector map) => template portion is a vector,
;; contents like the list in map
;; - (box map) => template portion is a box with substitution
;; - #s(ellipses elem count map) => template portion is an ellipses-generated list
;; - #s(ellipses-quote map) => template has a quoting ellipses
;; - #s(prefab v map) => template portion is a prefab
(define-struct ellipses (elem count rest) #:prefab #:omit-define-syntaxes)
(define-struct ellipses-quote (rest) #:prefab #:omit-define-syntaxes)
(define-struct prefab (key fields) #:prefab #:omit-define-syntaxes)
(define (datum->syntax* stx d)
(datum->syntax stx d stx stx stx))
(define (make-template-map tmpl const-leaf?)
(let loop ([tmpl tmpl]
[in-ellipses? #f])
(syntax-case tmpl ()
[(ellipses expr)
(and (not in-ellipses?)
(identifier? #'ellipses)
(free-identifier=? #'ellipses #'(... ...)))
(make-ellipses-quote (loop #'expr #t))]
[(expr ellipses . rest)
(and (not in-ellipses?)
(identifier? #'ellipses)
(free-identifier=? #'ellipses #'(... ...)))
(let-values ([(elem) (loop #'expr #f)]
[(rest count)
(let rloop ([rest #'rest][count 1])
(syntax-case rest ()
[(ellipses . rest)
(and (identifier? #'ellipses)
(free-identifier=? #'ellipses #'(... ...)))
;; keep going:
(rloop #'rest (add1 count))]
[else (values (loop rest #f) count)]))])
(make-ellipses elem count rest))]
[(a . b) (let ([a (loop #'a in-ellipses?)]
[b (loop #'b in-ellipses?)])
(and (or a b (not const-leaf?))
(cons a b)))]
[#(a ...) (let ([as (loop (syntax->list #'(a ...))
in-ellipses?)])
(and (or as (not const-leaf?))
(vector as)))]
[#&(a) (let ([as (loop #'a in-ellipses?)])
(and (or as (not const-leaf?))
(box as)))]
[a
(identifier? #'a)
(syntax-pattern-variable? (syntax-local-value #'a (lambda () #f)))]
[_
(let ([k (prefab-struct-key (syntax-e tmpl))])
(and k
(let ([as (loop (struct->list (syntax-e tmpl)) in-ellipses?)])
(and (or as (not const-leaf?))
(make-prefab k as)))))])))
(define (template-map-collect tmap template s->d leaf->d pvar->d)
(let loop ([tmap tmap][template template])
(cond
[(not tmap) (if (syntax? template)
(box (leaf->d template))
#f)]
[(eq? tmap #t) (pvar->d template)]
[(pair? tmap)
(if (syntax? template)
(vector (s->d template)
(loop (car tmap) (stx-car template))
(loop (cdr tmap) (stx-cdr template)))
(cons (loop (car tmap) (stx-car template))
(loop (cdr tmap) (stx-cdr template))))]
[(vector? tmap)
(cons (s->d template)
(loop (vector-ref tmap 0)
(vector->list (syntax-e template))))]
[(box? tmap)
(cons (s->d template)
(loop (unbox tmap)
(syntax-e template)))]
[(ellipses? tmap)
(let ([rest (let loop ([rest (stx-cdr template)]
[count (ellipses-count tmap)])
(if (zero? count)
rest
(loop (stx-cdr rest) (sub1 count))))])
(if (syntax? template)
(vector (s->d template)
(loop (ellipses-elem tmap) (stx-car template))
(loop (ellipses-rest tmap) rest))
(cons (loop (ellipses-elem tmap) (stx-car template))
(loop (ellipses-rest tmap) rest))))]
[(ellipses-quote? tmap)
(loop (ellipses-quote-rest tmap) (stx-car (stx-cdr template)))]
[(prefab? tmap)
(cons (s->d template)
(loop (prefab-fields tmap)
(struct->list (syntax-e template))))]
[else (error "template-map-collect fall-through")])))
(define (group-ellipses tmap template)
(let loop ([tmap tmap][template template])
(cond
[(boolean? tmap) template]
[(pair? tmap)
(let ([p (cons (loop (car tmap) (stx-car template))
(loop (cdr tmap) (stx-cdr template)))])
(if (syntax? template)
(datum->syntax* template p)
p))]
[(vector? tmap)
(datum->syntax* template
(list->vector
(loop (vector-ref tmap 0)
(vector->list (syntax-e template)))))]
[(box? tmap)
(datum->syntax* template
(box
(loop (unbox tmap)
(syntax-e template))))]
[(ellipses? tmap)
(let ([rest
(loop (ellipses-rest tmap)
(let loop ([rest (stx-cdr template)]
[count (ellipses-count tmap)])
(if (zero? count)
rest
(loop (stx-cdr rest) (sub1 count)))))]
[elem (loop (ellipses-elem tmap) (stx-car template))])
(let ([new `((,elem ,@(for/list ([i (in-range (ellipses-count tmap))])
#'(... ...)))
. ,rest)])
(if (syntax? template)
(datum->syntax* template new)
new)))]
[(ellipses-quote? tmap)
(datum->syntax* template
(list (stx-car template)
(loop (ellipses-quote-rest tmap) (stx-car (stx-cdr template)))))]
[(prefab? tmap)
(datum->syntax*
template
(apply
make-prefab-struct
(prefab-key tmap)
(loop (prefab-fields tmap)
(struct->list (syntax-e template)))))]
[else (error "group-ellipses fall-through")])))
(define (transform-template template-stx
#:save s->d
#:restore-stx d->s
#:leaf-save [leaf->d s->d]
#:leaf-restore-stx [leaf->s #'(lambda (data stx) stx)]
#:leaf-datum-stx [leaf-datum #'values]
#:pvar-save [pvar->d (lambda (x) #f)]
#:pvar-restore-stx [pvar->s #'(lambda (d s) s)]
#:cons-stx [pcons cons]
#:ellipses-end-stx [ellipses-end #'values]
#:constant-as-leaf? [const-leaf? #f])
(let* ([tmap (make-template-map template-stx const-leaf?)]
[grouped-template
;; Convert tmpl to group ...-created repetitions together,
;; so that `unwrap' can tell which result came from which
;; template:
(group-ellipses tmap template-stx)]
[data (template-map-collect tmap template-stx
s->d leaf->d pvar->d)])
#`(if #f
;; Process tmpl first, so that syntax errors are reported
;; usinf the original source.
(syntax #,template-stx)
;; Apply give d->s to result:
(template-map-apply '#,tmap
#,d->s #,leaf->s #,leaf-datum #,pvar->s #,pcons #,ellipses-end
'#,data
(syntax #,grouped-template)))))
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