(fast-fft) ( seq inverse? -- seq' )

Vocabulary

math.transforms.fft.private

Inputs

seq	an object
inverse?	an object

Outputs

seq'

an object

Definition

USING: kernel math math.constants math.functions sequences
sequences.extras ;

IN: math.transforms.fft.private

:: (fast-fft) ( seq inverse? -- seq' )
    seq length :> N seq even-indices inverse? (fft)
    :> evens seq odd-indices inverse? (fft)
    :> odds inverse? 1 -1 ? 2pi * N /
    :> angle N 2/ :> half N evens [| output |
        evens [| even k |
            k odds nth k angle * cis * :> odd even odd +
            inverse? [ 2 / ] when k output set-nth even odd -
            inverse? [ 2 / ] when k half + output set-nth
        ] each-index output
    ] new-like ; inline