The library provides Fast Fourier Transforms over finite fields with functionality for polynomial evaluation, polynomial interpolation, and computation of Lagrange polynomials.
In a finite field 
with 
elements. We can define a discrete Fourier
transform by selecting 
roots of unity 
.
import Protolude
import Data.Curve.Weierstrass.BN254 (Fr)
import Data.Pairing.BN254 (getRootOfUnity)
import FFT
k :: Int
k = 5
polySize :: Int
polySize = 2^k
leftCoeffs, rightCoeffs :: [Fr]
leftCoeffs = map fromIntegral [1..polySize]
rightCoeffs = map fromIntegral (reverse [1..polySize])
main :: IO ()
main = do
print (interpolate getRootOfUnity leftCoeffs)
print (fftMult getRootOfUnity leftCoeffs rightCoeffs)
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