zoomy_core.symbolic.canonicalise module

canonicalise(expr) — the structural-only normalisation pass.

Replaces the legacy _simplify_preserve_integrals (ins_generator.py:4409), including its 6-iteration fixpoint loop, with a single fixed-step pipeline of mathematically-trivial structural rewrites that cannot alter equality.

Steps (in order):

1. alpha_rename() — depth-keyed canonical bound-variable names so alpha-equivalent integrals match structurally.

2. sp.expand (Mul-over-Add only, kwargs-restricted; Integrals protected as Dummies during expand to keep their integrands intact).

3. drop_zero_integrand() — ∫0 dv = 0.

4. kill_zero_length_integral() — ∫_a^a dv = 0 (structural a == b only — no sp.simplify(lo - hi)).

5. zero_derivative_of_free_symbol() — ∂_v sym = 0 for free symbols distinct from v.

6. drop_zero_derivative_inner() — ∂_v 0 = 0.

7. merge_integrals_over_add() — combine sibling integrals with matching (limits, deriv-wrapper); required for sibling cancellations.

8. split_integral_over_add() — rest state: one logical equation term per Integral.

Sympy calls allowed: sp.Add (additive group axioms — combine like terms, drop zeros), sp.Mul/Pow constructors, sp.expand(_, mul=True, multinomial=False, …) (Mul-over-Add only), xreplace.

Sympy calls forbidden: sp.simplify, sp.cancel, sp.together, sp.factor, sp.collect, sp.powsimp, .doit(), sp.diff, sp.integrate.

The pass converges in one application — no fixpoint loop is needed because every step is a contraction on a well-founded ordering (number of Integral atoms, depth of nested integrands, count of zero Add-summands).

zoomy_core.symbolic.canonicalise.canonicalise(expr)

Normalise expr via the fixed structural pipeline.

Pure: canonicalise(canonicalise(x)) == canonicalise(x). Equality-preserving: canonicalise(x - y) == 0 iff x and y are structurally equal up to the canonicalisation rules (alpha-renaming of bound variables, Mul-over-Add distribution, Integral linearity, zero-collapse).