You cannot select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
typesetting/hyphenate/scribblings/hyphenate.scrbl

191 lines
10 KiB
Plaintext

11 years ago
#lang scribble/manual
@(require scribble/eval (for-label txexpr racket "../main.rkt" xml))
11 years ago
@(define my-eval (make-base-eval))
@(my-eval `(require (submod txexpr safe) (submod hyphenate safe) xml))
11 years ago
@title{Hyphenate}
11 years ago
@author[(author+email "Matthew Butterick" "mb@mbtype.com")]
11 years ago
11 years ago
@defmodule[#:multi (hyphenate (submod hyphenate safe))]
11 years ago
A simple hyphenation engine that uses the KnuthLiang hyphenation algorithm originally developed for TeX. This implementation is a port of Ned Batchelder's @link["http://nedbatchelder.com/code/modules/hyphenate.html"]{Python version}. I have added little to their work. Accordingly, I take little credit.
11 years ago
11 years ago
I originally put together this module to handle hyphenation for my web-based book @link["http://practicaltypography.com"]{Butterick's Practical Typography} (which I made with Racket & Scribble). Though support for CSS-based hyphenation in web browsers is @link["http://caniuse.com/#search=hyphen"]{still iffy}, soft hyphens work reliably well. But putting them into the text manually is a drag. Thus a module was born.
11 years ago
11 years ago
@section{Installation}
11 years ago
At the command line:
@verbatim{raco pkg install hyphenate}
11 years ago
11 years ago
After that, you can update the package like so:
11 years ago
@verbatim{raco pkg update hyphenate}
@section{Importing the module}
11 years ago
The module operates in two modes: fast and safe. Fast mode is the default, which you get by importing the module in the usual way: @code{(require hyphenate)}.
Safe mode enables the function contracts documented below. Use safe mode by importing the module as @code{(require (submod hyphenate safe))}.
11 years ago
@section{Interface}
11 years ago
@defproc[
(hyphenate
11 years ago
[xexpr xexpr/c]
11 years ago
[joiner (or/c char? string?) (integer->char #x00AD)]
11 years ago
[#:exceptions exceptions (listof string?) empty]
[#:min-length length (or/c integer? false?) 5]
[#:omit-word word-test (string? . -> . any/c) (λ(x) #f)]
[#:omit-string string-test (string? . -> . any/c) (λ(x) #f)]
[#:omit-txexpr txexpr-test (txexpr? . -> . any/c) (λ(x) #f)])
11 years ago
xexpr/c]
11 years ago
Hyphenate @racket[_xexpr] by calculating hyphenation points and inserting @racket[_joiner] at those points. By default, @racket[_joiner] is the soft hyphen (Unicode 00AD = decimal 173). Words shorter than @racket[#:min-length] @racket[_length] will not be hyphenated. To hyphenate words of any length, use @racket[#:min-length] @racket[#f].
11 years ago
11 years ago
@margin-note{The REPL displays a soft hyphen as @code{\u00AD}. But in ordinary use, you'll only see a soft hyphen when it appears at the end of a line or page as part of a hyphenated word. Otherwise it's not displayed. In most of the examples here, I use a standard hyphen for clarity (by adding @code{#\-} as an argument).}
11 years ago
@examples[#:eval my-eval
(hyphenate "ergo polymorphic")
(hyphenate "ergo polymorphic" #\-)
(hyphenate "ergo polymorphic" #:min-length 13)
(hyphenate "ergo polymorphic" #:min-length #f)
]
Because the hyphenation is based on an algorithm rather than a dictionary, it makes good guesses with unusual words:
@examples[#:eval my-eval
(hyphenate "scraunched strengths" #\-)
11 years ago
(hyphenate "RacketCon" #\-)
11 years ago
(hyphenate "supercalifragilisticexpialidocious" #\-)
]
11 years ago
Using the @racket[#:exceptions] keyword, you can pass hyphenation exceptions as a list of words with hyphenation points marked with regular hyphens (@racket["-"]). If an exception word contains no hyphens, that word will never be hyphenated.
11 years ago
11 years ago
@examples[#:eval my-eval
(hyphenate "polymorphic" #\-)
(hyphenate "polymorphic" #\- #:exceptions '("polymo-rphic"))
(hyphenate "polymorphic" #\- #:exceptions '("polymorphic"))
]
11 years ago
Knuth & Liang were sufficiently confident about their algorithm that they originally released it with only 14 exceptions: @italic{associate[s], declination, obligatory, philanthropic, present[s], project[s], reciprocity, recognizance, reformation, retribution}, and @italic{table}. Admirable bravado, but it's not hard to discover others that need adjustment.
11 years ago
@examples[#:eval my-eval
(hyphenate "wrong: columns signage lawyers" #\-)
(hyphenate "right: columns signage lawyers" #\-
#:exceptions '("col-umns" "sign-age" "law-yers"))
]
11 years ago
Overall, my impression is that the KnuthLiang algorithm is more likely to miss legitimate hyphenation points (i.e., generate false negatives) than create erroneous hyphenation points (i.e., false positives). This is good policy. Perfect hyphenation — that is, hyphenation that represents an exact linguistic syllabification of each word — is superfluous for typesetting. Hyphenation simply seeks to mark possible line-break and page-break locations for whatever layout engine is drawing the text. The ultimate goal is to permit more even text flow. Like horseshoes and hand grenades, close is good enough. And a word wrongly hyphenated is more likely to be noticed by a reader than a word inefficiently hyphenated.
11 years ago
11 years ago
For this reason, certain words can't be hyphenated algorithmically, because the correct hyphenation depends on meaning, not merely on spelling. For instance:
11 years ago
11 years ago
@examples[#:eval my-eval
(hyphenate "adder")
11 years ago
]
11 years ago
This is the right result. If you used @italic{adder} to mean the machine, it would be hyphenated @italic{add-er}; if you meant the snake, it would be @italic{ad-der}. Better to avoid hyphenation than to hyphenate incorrectly.
11 years ago
11 years ago
You can send HTML-style X-expressions through @racket[hyphenate]. It will recursively hyphenate the text strings, while leaving the tags and attributes alone, as well as non-hyphenatable material (like character entities and CDATA).
11 years ago
@examples[#:eval my-eval
11 years ago
(hyphenate '(p "strangely" (em "formatted" (strong "snowmen"))) #\-)
(hyphenate '(headline [[class "headline"]] "headline") #\-)
(hyphenate '(div "The (span epsilon) entity:" epsilon) #\-)
11 years ago
]
11 years ago
Don't send raw HTML or XML through @racket[hyphenate]. It can't distinguish tags and attributes from textual content, so everything will be hyphenated, thus goofing up your file. But you can easily convert your HTML or XML to an X-expression, hyphenate it, and then convert back.
11 years ago
@examples[#:eval my-eval
11 years ago
(define html "<body style=\"background: yellow\">Hello</body>")
(hyphenate html #\-)
(xexpr->string (hyphenate (string->xexpr html) #\-))
]
If you're working with HTML, be careful not to include any @code{<script>} or @code{<style>} blocks, which contain non-hyphenatable data. You can protect that data by using the @racket[#:omit-txexpr] keyword to specify a @racket[_txexpr-test]. The test will be applied to all tagged X-expressions (see @racket[txexpr?]). When @racket[_txexpr-test] evaluates to true, the item will be skipped.
@examples[#:eval my-eval
11 years ago
(hyphenate '(body "processing" (script "no processing")) #\-)
(hyphenate '(body "processing" (script "no processing")) #\-
#:omit-txexpr (λ(tx) (member (get-tag tx) '(script))))
]
You can also use @racket[#:omit-txexpr] to omit tagged X-expressions with particular attributes. This can be used to selectively suppress hyphenation at the markup level.
11 years ago
@examples[#:eval my-eval
(hyphenate '(p (span "processing") (span [[klh "no"]] "processing")) #\-)
(hyphenate '(p (span "processing") (span [[klh "no"]] "processing")) #\-
#:omit-txexpr (λ(tx) (and (attrs-have-key? tx 'klh)
(equal? (attr-ref tx 'klh) "no"))))
]
Similarly, you can use the @racket[#:omit-word] argument to avoid words that match @racket[_word-test]. Convenient if you want to prevent hyphenation of certain sets of words, like proper names:
11 years ago
@examples[#:eval my-eval
(hyphenate "Brennan Huff likes fancy sauce" #\-)
(define capitalized? (λ(word) (let ([letter (substring word 0 1)])
(equal? letter (string-upcase letter)))))
(hyphenate "Brennan Huff likes fancy sauce" #:omit-word capitalized? #\-)
11 years ago
]
11 years ago
Sometimes you need @racket[#:omit-word] to prevent unintended consequences. For instance, if you're using ligatures in CSS, certain groups of characters (fi, fl, ffi, et al.) will be replaced by a single glyph. That looks snazzy, but adding soft hyphens between any of these pairs will defeat the ligature substitution, creating inconsistent results. With @racket[#:omit-word], you can skip these words:
11 years ago
@margin-note{``Wouldn't it be better to exclude certain pairs of letters rather than whole words?'' Yes. But for now, that's not supported.}
11 years ago
@examples[#:eval my-eval
(hyphenate "Hufflepuff golfing final on Tuesday" #\-)
(define (ligs? word)
(ormap (λ(lig) (regexp-match lig word))
'("ff" "fi" "fl" "ffi" "ffl")))
(hyphenate "Hufflepuff golfing final on Tuesday" #:omit-word ligs? #\-)
]
11 years ago
11 years ago
@defproc[
(unhyphenate
11 years ago
[xexpr xexpr/c]
11 years ago
[joiner (or/c char? string?) @(integer->char #x00AD)]
[#:omit-word word-test (string? . -> . any/c) (λ(x) #f)]
[#:omit-string string-test (string? . -> . any/c) (λ(x) #f)]
[#:omit-txexpr txexpr-test (txexpr? . -> . any/c) (λ(x) #f)])
11 years ago
xexpr/c]
Remove @racket[_joiner] from @racket[_xexpr]. Like @racket[hyphenate], it works on nested X-expressions, and offers the same @racket[#:omit-] options.
11 years ago
@examples[#:eval my-eval
(hyphenate '(p "strangely" (em "formatted" (strong "snowmen"))) #\-)
(unhyphenate '(p "strange-ly" (em "for-mat-ted" (strong "snow-men"))) #\-)
]
11 years ago
11 years ago
A side effect of using @racket[hyphenate] is that soft hyphens (or whatever the @racket[_joiner] is) will be embedded in the output text. If you need to support copying of text, for instance in a GUI application, you'll probably want to strip out the hyphenation before the copied text is moved to the clipboard.
11 years ago
11 years ago
@examples[#:eval my-eval
(hyphenate "ribbon-cutting ceremony")
(unhyphenate (hyphenate "ribbon-cutting ceremony"))
]
11 years ago
11 years ago
Use this function cautiously — if @racket[_joiner] appeared in the original input to @racket[hyphenate], the output from @racket[unhyphenate] won't be the same string.
11 years ago
@examples[#:eval my-eval
(hyphenate "ribbon-cutting ceremony" #\-)
(unhyphenate (hyphenate "ribbon-cutting ceremony" #\-) #\-)
11 years ago
]
11 years ago
Keep in mind that soft hyphens could appear in your input string. Certain word processors allow users to @link["http://practicaltypography.com/optional-hyphens.html"]{insert soft hyphens} in their text.
11 years ago
@examples[#:eval my-eval
11 years ago
(hyphenate "True\u00ADType typefaces")
(unhyphenate (hyphenate "True\u00ADType typefaces"))
(hyphenate (unhyphenate "True\u00ADType typefaces") #\-)
11 years ago
]
11 years ago
@section{License & source code}
This module is licensed under the LGPL.
11 years ago
Source repository at @link["http://github.com/mbutterick/hyphenate"]{http://github.com/mbutterick/hyphenate}. Suggestions & corrections welcome.
11 years ago