last-grapheme ( str -- i )
Word and grapheme breaks

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Vocabulary
unicode

Inputs

str

a string

Outputs

i

an index

Word description
Finds the index of the start of the last grapheme of the string. This can be used to traverse the graphemes of a string backwards.

Definition

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

IN: unicode

:: last-grapheme ( str -- i )
    str length 1 - :> pos! pos 0 =
    [ 0 ] [
        str grapheme-class pos 1 - 0 max pos! 0 pos [a..b] [
            0 swap 1 + str <slice>
            grapheme-class dup rot grapheme-break?
        ] find-last drop ?1+ nip
    ] if ;