From 509116fddaf50d656408090746b12197da962c5d Mon Sep 17 00:00:00 2001
From: Matthew Butterick <mb@mbtype.com>
Date: Thu, 23 Jun 2016 22:21:57 -0700
Subject: [PATCH] simplify a loop

---
 hyphenate/hyphenate/private/core.rkt | 74 +++++++++++++---------------
 1 file changed, 34 insertions(+), 40 deletions(-)

diff --git a/hyphenate/hyphenate/private/core.rkt b/hyphenate/hyphenate/private/core.rkt
index 699680c7..772439c7 100644
--- a/hyphenate/hyphenate/private/core.rkt
+++ b/hyphenate/hyphenate/private/core.rkt
@@ -1,5 +1,5 @@
 #lang racket/base
-(require txexpr/base racket/string racket/list "params.rkt")
+(require txexpr/base racket/string racket/list sugar/list "params.rkt")
 (provide hyphenate unhyphenate word->hyphenation-points convert-exception-word string->hashpair)
 
 (module+ test
@@ -16,7 +16,7 @@
 (define (convert-exception-word exception)
   (define (make-key x) (format ".~a." (string-replace x "-" "")))
   (define (make-value x)
-    `(0 ,@(map (λ(x) (if (equal? x "-") 1 0)) (regexp-split #px"\\p{L}" x)) 0))
+    (append (list 0) (map (λ(x) (if (equal? x "-") 1 0)) (regexp-split #px"\\p{L}" x)) (list 0)))
   ;; use list instead of cons because value is itself a list, and consing will muddy the waters
   (list (make-key exception) (make-value exception)))
 
@@ -120,44 +120,41 @@
 
 ;; Find hyphenation points in a word. This is not quite synonymous with syllables.
 (define (word->hyphenation-points word 
-                                  [min-length-in #f] 
-                                  [min-left-length-in #f] 
-                                  [min-right-length-in #f])
+                                  [min-length #f] 
+                                  [min-left-length #f] 
+                                  [min-right-length #f])
   
-  (define min-length (or min-length-in default-min-length))
-  (define min-left-length (or min-left-length-in default-min-left-length))
-  (define min-right-length (or min-right-length-in default-min-right-length))
-  
-  (define (add-no-hyphen-zone points)
-    (let ([left-zeroes (min min-left-length (length points))]
-          [right-zeroes (min min-right-length (length points))])
-      ;; points is a list corresponding to the letters of the word.
-      (for/list ([(point idx) (in-indexed points)])
-                ;; to create a no-hyphenation zone of length n, zero out the first n-1 points
-                ;; and the last n points (because the last value in points is always superfluous)
-                (if (<= left-zeroes (add1 idx) (- (length points) right-zeroes))
-                    point
-                    0))))
-  
-  (define (make-pieces word)
-    (define-values (word-pieces last-piece) 
-      (for/fold ([word-pieces empty]
-                 [current-piece empty])
-                ;; explodes word into list of one-character strings (char list is slower)
-                ([str (in-list (regexp-match* #rx"." word))] 
-                 [point (in-list (add-no-hyphen-zone (make-points word)))])
-        (define updated-current-piece (cons str current-piece))
-        (if (even? point)
-            (values word-pieces updated-current-piece) ; even point denotes character
-            (values (cons (string-join (reverse updated-current-piece) "") word-pieces) empty)))) ; odd point denotes char + syllable
-    (reverse (cons (string-join (reverse last-piece) "") word-pieces)))
-  (if (and min-length (< (string-length word) min-length))
-      (list word)  
-      (make-pieces word)))
+  (cond
+    [(< (string-length word) (or min-length default-min-length)) (list word)]
+    [else
+     ;; points is a list corresponding to the letters of the word.
+     ;; to create a no-hyphenation zone of length n, zero out the first n-1 points
+     ;; and the last n points (because the last value in points is always superfluous)
+     (define word-points
+       (let* ([points (make-points word)]
+              [left-zeroes (min (or min-left-length default-min-left-length) (length points))]
+              [right-zeroes (min (or min-right-length default-min-right-length) (length points))])
+         (for/list ([(point idx) (in-indexed points)])
+                   (if (<= left-zeroes (add1 idx) (- (length points) right-zeroes))
+                       point
+                       0))))
+     
+     ;; odd-valued points in the pattern denote hyphenation points
+     (define odd-points (for/list ([(wp idx) (in-indexed word-points)]
+                                   #:when (odd? wp))
+                                  idx))
+     
+     ;; the hyphenation goes after the indexed letter, so add1 to the raw points for slicing
+     (define odd-points-plus-one (map add1 odd-points))
+     (for/list ([start (in-list (cons 0 odd-points-plus-one))]
+                [end (in-list (append odd-points-plus-one (list (string-length word))))])
+               (substring word start end))]))
+
 
 ;; joiner contract allows char or string; this coerces to string.
 (define (joiner->string joiner) (format "~a" joiner))
 
+
 (define (apply-proc proc x [omit-string (λ(x) #f)] [omit-txexpr (λ(x) #f)])
   (let loop ([x x])
     (cond
@@ -183,8 +180,7 @@
     (if (not (omit-word? word)) 
         (string-join (word->hyphenation-points word min-length min-left-length min-right-length) (joiner->string joiner)) 
         word))
-  (define (insert-hyphens text)
-    (regexp-replace* word-pattern text replacer))  
+  (define (insert-hyphens text) (regexp-replace* word-pattern text replacer))  
   (apply-proc insert-hyphens x omit-string? omit-txexpr?))
 
 
@@ -197,7 +193,5 @@
     (if (not (omit-word? word)) 
         (string-replace word (joiner->string joiner) "")
         word))
-  (define (remove-hyphens text)
-    (regexp-replace* word-pattern text replacer))
-  
+  (define (remove-hyphens text) (regexp-replace* word-pattern text replacer))
   (apply-proc remove-hyphens x omit-string? omit-txexpr?))