first-grapheme ( entire-str start -- i )
Word and grapheme breaks

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first-grapheme-from ( start str -- i )

Vocabulary
unicode

Inputs

entire-str	a string
start	a string

Outputs

i

an index

Word description
Finds the length of the first grapheme of the string. This can be used repeatedly to efficiently traverse the graphemes of the string, using slices.

Definition

USING: kernel math math.order ranges sequences
unicode.breaks.private ;

IN: unicode

:: first-grapheme ( entire-str start -- i )
    start :> pos! entire-str length :> str-len 0 pos 1 +
    entire-str <slice> grapheme-class pos 1 + str-len 1 - min
    pos! pos str-len 1 - [a..b] [
        1 + 0 swap entire-str <slice>
        grapheme-class dup rot swap grapheme-break?
    ] find drop nip [ 1 + ] [ str-len start - ] if* ;