pub fn walsh_spectrum(truth: &[bool]) -> Option<Vec<i64>>Expand description
The Walsh spectrum of a Boolean function given as its 2ⁿ-entry truth table: Ŵ(w) = Σₓ (−1)^{C(x) ⊕ ⟨w,x⟩}, the signed correlation of C with every linear function ⟨w,x⟩. Index w is the linear
mask (bit i selects variable i). None if the length is not a positive power of two.