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23 lines
817 B
Racket
23 lines
817 B
Racket
#lang racket/base
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(require racket/contract)
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(require "coerce.rkt" "container.rkt" "len.rkt" "exception.rkt")
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(provide starts-with? ends-with? stringish?)
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;; stringish: data type that can be trivially converted to string
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;; todo: merge this with pathish
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(define/contract (stringish? x)
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(any/c . -> . boolean?)
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(try (->boolean (->string x)) (except [exn:fail? (λ(e) #f)])))
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;; python-style string testers
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(define/contract (starts-with? str starter)
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(stringish? stringish? . -> . boolean?)
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(let ([str (->string str)]
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[starter (->string starter)])
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(and (<= (len starter) (len str)) (equal? (get str 0 (len starter)) starter))))
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(define/contract (ends-with? str ender)
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(string? string? . -> . boolean?)
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(and (<= (len ender) (len str)) (equal? (get str (- (len str) (len ender)) 'end) ender))) |