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25 lines
1.4 KiB
Racket
25 lines
1.4 KiB
Racket
#lang racket/base
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(provide (all-defined-out))
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(define (split-metas x meta-key)
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(apply hasheq
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(let loop ([x (if (syntax? x) (syntax->datum x) x)])
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(cond
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[(list? x) (cond
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[(and (= (length x) 3) (eq? (car x) meta-key))
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(unless (symbol? (cadr x))
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(raise-argument-error 'define-meta "valid meta key" (cadr x)))
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(cdr x)] ; list with meta key and meta value
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[else (apply append (map loop x))])]
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[else null]))))
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(module+ test
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(require rackunit)
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(check-equal? (split-metas 'root 'define-meta) (hasheq))
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(check-equal? (split-metas '(root) 'define-meta) (hasheq))
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(check-exn exn:fail:contract? (λ () (split-metas '(root (define-meta 42 "bar")) 'define-meta)))
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(check-equal? (split-metas '(root (div #:kw #f (define-meta foo "bar") "hi") "zim" (define-meta foo "boing") "zam") 'define-meta) '#hasheq((foo . "boing")))
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(check-equal? (split-metas '(root (div #:kw #f (define-meta foo 'bar) "hi") "zim" (define-meta foo 'boing) "zam") 'define-meta) '#hasheq((foo . 'boing)))
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(check-equal? (split-metas #'(root (define-meta dog "Roxy") (define-meta dog "Lex")) 'define-meta) '#hasheq((dog . "Lex")))
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(check-equal? (split-metas #'(root (define-meta dog "Roxy") (div (define-meta dog "Lex"))) 'define-meta) '#hasheq((dog . "Lex")))) |