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# issue #23855, not entirely fixed
import std/bitops
const WordBitWidth = sizeof(pointer) * 8
func wordsRequired*(bits: int): int {.inline.} =
const divShiftor = fastLog2(uint32(WordBitWidth))
result = (bits + WordBitWidth - 1) shr divShiftor
type
Algebra* = enum
BLS12_381
BigInt*[bits: static int] = object
limbs*: array[wordsRequired(bits), uint]
Fr*[Name: static Algebra] = object
residue_form*: BigInt[255]
Fp*[Name: static Algebra] = object
residue_form*: BigInt[381]
FF*[Name: static Algebra] = Fp[Name] or Fr[Name]
template getBigInt*[Name: static Algebra](T: type FF[Name]): untyped =
## Get the underlying BigInt type.
typeof(default(T).residue_form)
type
EC_ShortW_Aff*[F] = object
## Elliptic curve point for a curve in Short Weierstrass form
## y² = x³ + a x + b
##
## over a field F
x*, y*: F
func bits*[Name: static Algebra](T: type FF[Name]): static int =
T.getBigInt().bits
# ------------------------------------------------------------------------------
type
ECFFT_Descriptor*[EC] = object
## Metadata for FFT on Elliptic Curve
order*: int
rootsOfUnity*: ptr UncheckedArray[BigInt[Fr[EC.F.Name].bits()]] # Undeclared identifier `Name`
func new*(T: type ECFFT_Descriptor): T =
discard
# ------------------------------------------------------------------------------
template getBits[bits: static int](x: ptr UncheckedArray[BigInt[bits]]): int = bits
proc main() =
let ctx = ECFFT_Descriptor[EC_ShortW_Aff[Fp[BLS12_381]]].new()
doAssert getBits(ctx.rootsOfUnity) == 255
doAssert ctx.rootsOfUnity[0].limbs.len == wordsRequired(255)
main()
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