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55 lines
2.4 KiB
Racket
55 lines
2.4 KiB
Racket
#lang racket/base
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(provide (all-defined-out))
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;; (string->symbol (format "~a" #\u200B))
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(define splice-signal-tag '@)
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(define (attrs? x)
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(and (list? x)
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(andmap (λ (xi)
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(and (list? xi)
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(= (length xi) 2)
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(symbol? (car xi))
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(string? (cadr xi)))) x)))
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(define (splice x [splicing-tag splice-signal-tag])
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; (listof txexpr-elements?) . -> . (listof txexpr-elements?))
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(define spliceable? (λ (x) (and (pair? x) (eq? (car x) splicing-tag))))
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(define not-null-string? (λ (x) (not (and (string? x) (zero? (string-length x))))))
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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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(apply append (map (λ (x) (let ([proc (if (spliceable? x) ; drop the splice-signal from front with `cdr`
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cdr
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list)]
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[x (if (not (attrs? x)) ; don't recur on attributes, so null strings are not spliced within
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(loop x)
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x)])
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(proc x))) (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 (,splice-signal-tag 2 "" (,splice-signal-tag 3 (div 4 (,splice-signal-tag 5))) 6) "" 7)))
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'((div 1 2 3 (div 4 5) 6 7)))
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(check-equal? (splice `((,splice-signal-tag 1 (,splice-signal-tag 2 "" (,splice-signal-tag 3 (div 4 (,splice-signal-tag 5))) 6) "" 7)))
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'(1 2 3 (div 4 5) 6 7))
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(check-equal? (splice `((,splice-signal-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 `((,splice-signal-tag "str"))) '("str")))
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(define (strip-empty-attrs x)
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(let loop ([x x])
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(if (list? x)
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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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(map loop (filter (λ (x) (not (null? x))) 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"))) |