USING: help.syntax help.markup strings ;
IN: unicode.breaks

ABOUT: "unicode.breaks"

ARTICLE: "unicode.breaks" "Word and grapheme breaks"
"The " { $vocab-link "unicode.breaks" "unicode.breaks" } " vocabulary partially implements Unicode Standard Annex #29. This provides for segmentation of a string along grapheme and word boundaries. In Unicode, a grapheme, or a basic unit of display in text, may be more than one code point. For example, in the string \"e\\u000301\" (where U+0301 is a combining acute accent), there is only one grapheme, as the acute accent goes above the e, forming a single grapheme. Word breaks, in general, are more complicated than simply splitting by whitespace, and the Unicode algorithm provides for that."
$nl "Operations for graphemes:"
{ $subsection first-grapheme }
{ $subsection last-grapheme }
{ $subsection >graphemes }
{ $subsection string-reverse }
"Operations on words:"
{ $subsection first-word }
{ $subsection >words } ;

HELP: first-grapheme
{ $values { "str" string } { "i" "an index" } }
{ $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." } ;

HELP: last-grapheme
{ $values { "str" string } { "i" "an index" } }
{ $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." } ;

HELP: >graphemes
{ $values { "str" string } { "graphemes" "an array of strings" } }
{ $description "Divides a string into a sequence of individual graphemes." } ;

HELP: string-reverse
{ $values { "str" string } { "rts" string } }
{ $description "Reverses a string, leaving graphemes in-tact." } ;

HELP: first-word
{ $values { "str" string } { "i" "index" } }
{ $description "Finds the length of the first word in the string." } ;

HELP: >words
{ $values { "str" string } { "words" "an array of strings" } }
{ $description "Divides the string up into words." } ;