pub fn pi_groups(dims: &[Dimension]) -> Vec<Vec<i32>>Expand description
Integer basis of the nullspace of the dimension matrix of dims.
Each returned vector e (length dims.len()) satisfies ∑ eᵢ · dim(xᵢ) = 0, i.e. the monomial
∏ xᵢ^{eᵢ} is dimensionless. The basis has n − rank vectors; for fully-dimensionally-independent
inputs it is empty. Returned vectors are reduced (gcd 1) with a leading-positive sign convention.