Snowball

routines (
   prelude postlude mark_regions
   RV R1 R2
   standard_suffix
)

externals ( stem )

booleans ( is_verb is_noun )

groupings ( v )

stringescapes {}

stringdef a  hex 'E1'
stringdef e  hex 'E9'
stringdef i  hex 'ED'
stringdef o  hex 'F3'
stringdef u  hex 'FA'

define v 'aeiou{a}{e}{i}{o}{u}'

define mark_regions as (

    $pV = limit
    $p1 = limit
    $p2 = limit

    do (
        gopast v  gopast non-v  setmark pV
    )
    do (
        gopast v  gopast non-v  setmark p1
        gopast v  gopast non-v  setmark p2
    )
)

define prelude as (
    test repeat (
        [substring] among(
            'qu' (hop 2)
            '' (next)
        )
    )
)

define postlude as repeat (

    [substring] among(
        '{a~}' (<- 'a')
        '{e~}' (<- 'e')
        '{i~}' (<- 'i')
        '{o~}' (<- 'o')
        '{u~}' (<- 'u')
    )
)

define RV as $pV <= cursor
define R1 as $p1 <= cursor
define R2 as $p2 <= cursor

define standard_suffix as (
    [substring] R1 among(
        'ances' 'ancias' 'ancias' 'logias' 'encias' 'amente'
        'ismos' 'ables' 'ibles' 'istas' 'adora' 'acion'
        'antes' 'ancia' 'encia' 'mente' 'ancia' 'eria'
            (delete)
    )
)

define stem as (
    do prelude
    do mark_regions
    backwards
        do standard_suffix
    do postlude
)