const preallocLimbs = (preallocTarget + _W - 1) / _W // NewNat returns a new nat with a size of zero, just like new(Nat), but with // the preallocated capacity to hold a number of up to preallocTarget bits. // NewNat inlines, so the allocation can live on the stack. func NewNat() *Nat { limbs := make([]uint, 0, preallocLimbs) return &Nat{limbs} } // expand expands x to n limbs, leaving its value unchanged. func (x *Nat) expand(n int) *Nat { if len(x.limbs) > n { panic("bigmod: internal error: shrinking...