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POWhat's the correct algorithm to determine number of user-perceived-characters?
 

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  1. POWhat's the correct algorithm to determine number of user-perceived-characters?
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    <p>I have the task of counting the number of perceived characters in an input. The input is a <em>group</em> of ints (we can think of it as an <code>int[]</code>) which represents Unicode code points.</p> <p><a href="http://docs.oracle.com/javase/7/docs/api/java/text/BreakIterator.html#getCharacterInstance%28%29" rel="nofollow noreferrer">java.text.BreakIterator.getCharacterInstance()</a> is not allowed. (I mean their formula is allowed and is what I wanted, but weaving through their source code and state tables got me nowhere >.&lt;)</p> <p>I was wondering what's the correct algorithm to count the number of grapheme-clusters given some code points?</p> <p><a href="http://en.wikipedia.org/wiki/Combining_character#Unicode_ranges" rel="nofollow noreferrer">Initially</a>, I'd thought that all I have to do is to combine all occurences of:</p> <ol> <li><p><code>U+0300 – U+036F</code> (combining diacritical marks)</p></li> <li><p><code>U+1DC0 – U+1DFF</code> (combining diacritical marks supplement)</p></li> <li><p><code>U+20D0 – U+20FF</code> (combining diacritical marks for symbols)</p></li> <li><p><code>U+FE20 - U+FE2F</code> (combining half marks)</p></li> </ol> <p>into the previous non-diacritic-mark.</p> <p>However I've <a href="http://en.wikipedia.org/wiki/Mapping_of_Unicode_characters#Noncharacters" rel="nofollow noreferrer">realised</a> that prior to that operation, I have to first remove all non-characters as well. </p> <p>This includes:</p> <ol> <li><p><code>U+FDD0 - U+FDEF</code></p></li> <li><p>The last two code points of every plane </p></li> </ol> <p>But there seems to be more things to do. <a href="http://www.unicode.org/reports/tr29/#Table_Sample_Grapheme_Clusters" rel="nofollow noreferrer">Unicode.org</a> states we need to include <code>U+200C</code> (zero-width non joiner) and <code>U+200D</code> (zero width joiner) as part of the set of continuing characters <a href="http://www.unicode.org/reports/tr29/#Table_Sample_Grapheme_Clusters" rel="nofollow noreferrer">(source)</a>.</p> <p>Besides that, it talks about a couple more things but the entire topic is treated in an abstract way. For example, what are the code point ranges for <strong>spacing combining marks</strong>, <strong>hangul jamo characters that forms hangul syllables</strong>?</p> <p>Does anyone know the correct algorithm to count the number of grapheme-clusters given an <code>int[]</code> of code points?</p>
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    1. COIn [this answer](http://stackoverflow.com/a/6806203/68063) I gave a reference to the Unicode algorithm for splitting text into grapheme clusters, and demonstrated how to implement some of it in Python.
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      1. USGareth Rees
    2. CO@GarethRees I think that there's many important steps missing in that answer to do a correct *user-perceived-character* check (correct me if I'm wrong).
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      1. POWhat's the correct algorithm to determine number of user-perceived-characters?
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    3. COCan you use the ICU `BreakIterator`? http://icu-project.org/apiref/icu4j/com/ibm/icu/text/BreakIterator.html
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      1. USJoni
 

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