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25 lines
1.3 KiB
Racket
25 lines
1.3 KiB
Racket
#lang racket/base
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(require racket/match
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racket/list)
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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 values) x)])
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(match x
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[(list (== meta-key eq?) key val)
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(unless (symbol? key)
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(raise-argument-error 'define-meta "valid meta key" key))
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(list key val)]
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[(? list? xs) (append-map loop xs)]
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[_ 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")))) |