mutable Tutorial

Use mutable when code needs explicit control over intermediate allocation or step-by-step construction. The mathematical semantics match immut, but mutation is limited to setters, clear, and _inplace methods.

Dense Univariate DensePolynomial

let p = @mutable.DensePolynomial::from_coefficients([1, 2, 3])
let snapshot = p.copy()

p.set_coefficient(1, 5)
p.add_inplace(@mutable.DensePolynomial::from_coefficients([-1, -5, -3]))

snapshot still represents 1 + 2x + 3x^2. p is updated and then canonicalized to zero.

Ordinary operators do not mutate the receiver:

let p = @mutable.DensePolynomial::from_coefficients([1, 2])
let q = p * p
let unchanged = p.to_coefficients()

q is a new polynomial and unchanged is [1, 2].

Converting To And From immut

let imm = @immut.DensePolynomial::from_coefficients([1, 0, 1])
let mut_poly = @mutable.DensePolynomial::from_immut(imm)
mut_poly.set_coefficient(0, 2)
let back = mut_poly.to_immut()

Conversions produce independent values.

Multivariate Term Arrays

let p = @mutable.TermPolynomial::from_array([([1U], 2)])
p.add_term_inplace(@mutable.ExponentVector::from_array([1U, 0]), -2)
let is_zero = p.size() == 0

The two exponent vectors canonicalize to the same key, so the terms cancel.

Sparse Map Representation

let x = @mutable.ExponentVector::from_array([1U])
let p = @mutable.SparsePolynomial::new()
p.set_coefficient(x, 3)
p.add_term_inplace(x, -1)
let coeff = p.get(x)

coeff is Some(2). Setting a coefficient to zero removes the term.

Guidance

• Use _inplace only when mutating the receiver is intentional.
• Prefer immut when code relies on sharing old values.
• Use to_immut and from_immut at API boundaries to isolate mutable state.