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26 lines
821 B
Racket
26 lines
821 B
Racket
#lang racket/base
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(require "define.rkt" "coerce.rkt")
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(define+provide+safe (starts-with? str starter)
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(string? string? . -> . coerce/boolean?)
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(let ([str (->string str)]
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[starter (->string starter)])
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(and (<= (string-length starter) (string-length str))
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(equal? (substring str 0 (string-length starter)) starter))))
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(define+provide+safe (ends-with? str ender)
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(string? string? . -> . coerce/boolean?)
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(let ([str (->string str)]
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[ender (->string ender)])
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(and (<= (string-length ender) (string-length str))
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(equal? (substring str (- (string-length str) (string-length ender)) (string-length str)) ender))))
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(define+provide+safe (capitalized? str)
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(string? . -> . coerce/boolean?)
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(let ([str (->string str)])
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(char-upper-case? (car (string->list str)))))
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