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- #!/usr/bin/env gosh
- ;; In the dictionary, find the longest ordered word
- ;; An ordered word is one which has its letter in alphabetical order
- (import (scheme base)
- (scheme char)
- (scheme file)
- (scheme write)
- (srfi 95)) ;; For 'sorted?'
- (define dictionary
- (open-input-file "/usr/share/dict/words"))
- (define (next-word)
- ;; Words with punctuation will be automatically rejected
- (let ((next (read-line dictionary)))
- (if (eof-object? next)
- (begin
- (close-input-port dictionary)
- next)
- (string-downcase next))))
- (define-record-type type-word-list
- (word-list size contents)
- word-list?
- (size wl-size)
- (contents wl-contents))
- (define (update-wl wl word)
- (if (and (>= (string-length word) (wl-size wl))
- (sorted? (string->list word) char<?))
- (word-list (string-length word)
- (if (> (string-length word) (wl-size wl))
- (list word)
- (cons word (wl-contents wl))))
- wl))
- (define (make-null-wl)
- (word-list 0 '("")))
- (define longest-sorted
- (let loop ((wl (make-null-wl))
- (next (next-word)))
- (if (eof-object? next)
- wl
- (loop (update-wl wl next)
- (next-word)))))
- (write (wl-contents longest-sorted))
- (newline)
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