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typesetting/hyphenate/main.rkt

167 lines
6.9 KiB
Racket

#lang racket/base
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(require racket/string racket/list racket/contract racket/vector racket/bool)
(require "data.rkt" "readability.rkt")
(module+ test (require rackunit))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Hyphenate.rkt
;;; Racket port of Ned Batchelder's hyphenate.py
;;; http://nedbatchelder.com/code/modules/hyphenate.html
;;; (in the public domain)
;;; which in turn was an implementation
;;; of the Liang hyphenation algorithm in TeX
;;; (also in the public domain)
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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(provide hyphenate hyphenatef unhyphenate)
;; global data, define now but set! them later (because they're potentially big & slow)
(define exceptions #f)
(define pattern-tree #f)
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(define default-min-length 5)
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(define default-joiner (integer->char #x00AD))
;; Convert the hyphenated pattern into a point array for use later.
(define/contract (list->exceptions exn-strings)
((listof string?) . -> . hash?)
(define (make-key x)
(string-replace x "-" ""))
(define (make-value x)
(list->vector (cons 0 (map (λ(x) (if (equal? x "-") 1 0)) (regexp-split #px"[a-z]" x)))))
(make-hash (map (λ(x) (cons (make-key x) (make-value x))) exn-strings)))
;; A word is a string without whitespace.
(define/contract (word? x)
(any/c . -> . boolean?)
(->boolean (regexp-match #px"^\\S+$" x)))
(module+ test
(check-true (word? "Foobar"))
(check-true (word? "foobar"))
(check-true (word? "foo-bar"))
(check-false (word? "foo bar")))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Helper functions
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Convert a pattern like 'a1bc3d4' into a string of chars 'abcd'
;; and a list of points [ 1, 0, 3, 4 ].
(define (make-pattern-tree pattern-data)
(define tree (make-hash))
;; Insert the pattern into the tree. Each character finds a dict
;; another level down in the tree, and leaf nodes have the list of
;; points.
(define (insert-pattern pat)
(let* ([chars (regexp-replace* #px"[0-9]" pat "")]
;; regexp returns list of strings
[points (map (λ(x) (if (> (len x) 0) (string->number x) 0)) (regexp-split #px"[.a-z]" pat))]
[tree tree])
(for ([char chars])
(when (not (hash-has-key? tree char))
(hash-set! tree char (make-hash)))
(set! tree (hash-ref tree char)))
(hash-set! tree empty points)))
(map insert-pattern pattern-data)
tree)
(define/contract (make-points word)
(word? . -> . vector?)
(define/contract (make-zeroes points)
(vector? . -> . vector?)
; controls hyphenation zone from edges of word
; todo: parameterize this setting
; todo: does this count end-of-word punctuation? it shouldn't.
(map (λ(i) (vector-set! points i 0)) (list 1 2 (- (len points) 2) (- (len points) 3)))
points)
(let* ([word (string-downcase word)]
[points
(if (hash-has-key? exceptions word)
(hash-ref exceptions word)
(let* ([work (string-append "." (->string word) ".")]
[points (make-vector (add1 (len work)) 0)])
(for ([i (len work)])
(let ([tree pattern-tree])
(for ([char (substring work i (len work))]
#:break (not (hash-has-key? tree char)))
(set! tree (hash-ref tree char))
(when (hash-has-key? tree empty)
(let ([point (hash-ref tree empty)])
(for ([j (len point)])
(vector-set! points (+ i j) (max (vector-ref points (+ i j)) (list-ref point j)))))))))
points))])
; make-zeroes controls minimum hyphenation distance from edge.
; todo: dropping first 2 elements is needed for mysterious reasons to be documented later
(vector-drop (make-zeroes points) 2)))
;; Find hyphenatable pieces of a word. This is not quite synonymous with syllables.
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(define/contract (word->pieces word [min-length default-min-length])
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((word?) ((or/c integer? false?)) . ->* . (listof string?))
(define (make-pieces word)
(define word-dissected (flatten (for/list ([char word]
[point (make-points word)])
(if (even? point)
char ; even point denotes character
(cons char 'syllable))))) ; odd point denotes char + syllable
(map list->string (splitf-at* word-dissected symbol?)))
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(if (and min-length (< (len word) min-length))
(list word)
(make-pieces word)))
;; Hyphenate using a filter procedure.
;; Theoretically possible to do this externally,
;; but it would just mean doing the regexp-replace twice.
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(define/contract (hyphenatef text proc [joiner default-joiner] #:exceptions [extra-exceptions '()] #:min-length [min-length default-min-length])
((string? procedure?) ((or/c char? string?) #:exceptions (listof word?) #:min-length (or/c integer? false?)) . ->* . string?)
;; set up module data
(set! exceptions (list->exceptions (append default-exceptions (map ->string extra-exceptions))))
(when (not pattern-tree) (set! pattern-tree (make-pattern-tree default-patterns)))
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(regexp-replace* #px"\\w+" text (λ(word) (if (proc word) (string-join (word->pieces word min-length) (->string joiner)) word))))
;; Default hyphenate function.
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(define/contract (hyphenate text [joiner default-joiner] #:exceptions [extra-exceptions '()] #:min-length [min-length default-min-length])
((string?) ((or/c char? string?) #:exceptions (listof word?) #:min-length (or/c integer? false?)) . ->* . string?)
(hyphenatef text (λ(x) #t) joiner #:exceptions extra-exceptions #:min-length min-length))
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(define/contract (unhyphenate text [joiner default-joiner])
((string?) ((or/c char? string?)) . ->* . string?)
(string-replace text (->string joiner) ""))
(module+ test
(check-equal? (hyphenate "polymorphism") "poly\u00ADmor\u00ADphism")
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(check-equal? (hyphenate "polymorphism" #:min-length 100) "polymorphism")
(check-equal? (hyphenate "ugly" #:min-length 1) "ug\u00ADly")
(check-equal? (unhyphenate "poly\u00ADmor\u00ADphism") "polymorphism")
(check-equal? (hyphenatef "polymorphism" (λ(x) #f)) "polymorphism")
(check-equal? (hyphenate "polymorphism" #\-) "poly-mor-phism")
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(check-equal? (hyphenate "polymorphism" "foo") "polyfoomorfoophism")
(check-equal? (unhyphenate "polyfoomorfoophism" "foo") "polymorphism")
(check-equal? (hyphenate "polymorphism" #\* #:exceptions '("polymo-rphism")) "polymo*rphism")
(check-equal? (hyphenate "circular polymorphism squandering") "cir\u00ADcu\u00ADlar poly\u00ADmor\u00ADphism squan\u00ADder\u00ADing")
(check-equal? (hyphenate "present project") "present project") ; exception words
;; test these last so exceptions have been set up already
(check-equal? (word->pieces "polymorphism") '("poly" "mor" "phism"))
(check-equal? (word->pieces "present") '("present"))) ; exception word