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69 lines
2.5 KiB
Racket
69 lines
2.5 KiB
Racket
#lang racket/base
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(require racket/match
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racket/list
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"constants.rkt")
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(provide (all-defined-out))
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;; (string->symbol (format "~a" #\u200B))
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(define (attrs? x)
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(match x
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[(list (list (? symbol?) (? string?)) ...) #true]
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[_ #false]))
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(define (null-string? x) (equal? x ""))
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(define ((spliceable? splicing-tag) x)
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(match x
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[(cons (== splicing-tag eq?) _) #true]
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[_ #false]))
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(define (splice x [splicing-tag pollen-splicing-tag])
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; (listof txexpr-elements?) . -> . (listof txexpr-elements?))
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(let loop ([x x])
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(if (list? x) ; don't exclude `attrs?` here, because it will exclude valid splice input like '((@ "foo"))
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(append-map (λ (x)
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; drop the splice-signal from front with `rest`
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; don't recur on attributes, so null strings are not spliced within
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(define proc (if ((spliceable? splicing-tag) x) rest list))
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(proc (if (attrs? x) x (loop x))))
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(filter-not null-string? x))
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x)))
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(module+ test
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(require rackunit)
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(check-equal? (splice `((div 1 (,pollen-splicing-tag 2 "" (,pollen-splicing-tag 3 (div 4 (,pollen-splicing-tag 5))) 6) "" 7)))
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'((div 1 2 3 (div 4 5) 6 7)))
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(check-equal? (splice `((,pollen-splicing-tag 1 (,pollen-splicing-tag 2 "" (,pollen-splicing-tag 3 (div 4 (,pollen-splicing-tag 5))) 6) "" 7)))
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'(1 2 3 (div 4 5) 6 7))
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(check-equal? (splice `((,pollen-splicing-tag "foo" "" "bar"))) '("foo" "bar"))
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(check-equal? (splice null) null)
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(check-equal? (splice '(a ((href "")(foo "bar")) "zam")) '(a ((href "")(foo "bar")) "zam"))
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(check-equal? (splice `((,pollen-splicing-tag "str"))) '("str")))
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;; this will strip all empty lists.
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;; in practice, they would only appear in attrs position
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(define (strip-empty-attrs x)
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(let loop ([x x])
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(if (pair? x)
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(map loop (filter-not null? x))
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x)))
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(module+ test
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(check-equal? (strip-empty-attrs '(p ())) '(p))
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(check-equal? (strip-empty-attrs '(p () "foo")) '(p "foo"))
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(check-equal? (strip-empty-attrs '(p () (em () "foo") "bar")) '(p (em "foo") "bar")))
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;; used with pollen/markup to suppress void arguments,
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;; consistent with how pollen/pre and pollen/markdown handle them
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(define (remove-voids x)
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(let loop ([x x])
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(if (pair? x)
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(map loop (filter-not void? x))
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x)))
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(module+ test
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(check-equal? (remove-voids (list 1 2 3 (void))) '(1 2 3))
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(check-equal? (remove-voids (list 1 (void) 2 3 (list 4 5 6 (void)))) '(1 2 3 (4 5 6)))
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(check-equal? (remove-voids (void)) (void))) |