slice-parameters ( selector size -- start count step )

Vocabulary

arrays.shaped.private

Inputs

selector	an object
size	an object

Outputs

start	an object
count	an object
step	an object

Definition

USING: accessors arrays.shaped kernel math math.order ;

IN: arrays.shaped.private

:: slice-parameters ( selector size -- start count step )
    selector step>> [ ] [ 1 ] if* :> step step integer?
    [ step zero? not ] [ f ] if
    [ selector invalid-shaped-slice ] unless step 0 > [
        selector start>> size 0 size 0 slice-bound
        selector stop>> size 0 size size slice-bound
    ] [
        selector start>> size -1 size 1 - size 1 - slice-bound
        selector stop>> size -1 size 1 - -1 slice-bound
    ] if :> ( start stop ) start stop start - step sgn * 0 max
    step abs 1 - + step abs /i step ;