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26 lines
1.3 KiB
Racket
26 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 'define-meta])
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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)
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(raise-argument-error meta-key "meta value missing" key)]
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[(list (== meta-key eq?) key val)
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(unless (symbol? key)
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(raise-argument-error meta-key "valid meta key" key))
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(list (cons 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) null)
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(check-equal? (split-metas '(root)) null)
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(check-exn exn:fail:contract? (λ () (split-metas '(root (define-meta 42 "bar")))))
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(check-equal? (split-metas '(root (div #:kw #f (define-meta foo "bar") "hi") "zim" (define-meta foo "boing") "zam")) '((foo . "bar") (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")) '((foo . 'bar) (foo . 'boing)))
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(check-equal? (split-metas #'(root (define-meta dog "Roxy") (define-meta dog "Lex"))) '((dog . "Roxy") (dog . "Lex")))
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(check-equal? (split-metas #'(root (define-meta dog "Roxy") (div (define-meta dog "Lex")))) '((dog . "Roxy") (dog . "Lex")))) |