feat: introduce Differential operator and deprecate D - #27
Open
s-celles wants to merge 5 commits into
Open
Conversation
s-celles
commented
May 10, 2026
s-celles
commented
Collaborator
- Add Giac.Differential, the canonical SciML/MTK-style partial-differentiation operator. Differential(var)(operand) accepts function-form expressions (returns DerivativeExpr) and bare GiacExpr operands (returns plain GiacExpr via Commands.diff), matching SymPy.jl's diff(expr, var) and Symbolics.jl's Differential. Two-argument shorthand Differential(var, n) matches Symbolics' Differential(x, 2).
- Widen DerivativeExpr internally to steps::Vector{Tuple{String, Int}}. Adjacent same-variable steps collapse, mixed variables compose freely so cross/higher-order partials work uniformly.
- Deprecate D: every D(...) call shape now emits Base.depwarn pointing to Differential. Multi-arg D(f) on a function f(x, y) raises ArgumentError instead of silently picking the first variable. D removal scheduled for the next published release.
- Display: derivative orders >= 4 render as f^(n)(x) rather than long prime strings; DerivativePoint string output keeps prime form (GIAC consumes it in initial conditions).
- Docs: new migration guide (docs/src/migration/d_to_differential.md); Differential coverage in mathematics/calculus.md; ODE doc rewritten to lead with Differential; new Pluto notebook examples/07_odes_pdes.jl with worked symbolic ODE/PDE walkthroughs; CHANGELOG [Unreleased] entries under Added / Deprecated / Changed.
- Tests: 9078 passing under Pkg.test() (+91 over baseline), zero failing regressions. Doc build clean.
- Add Giac.Differential, the canonical SciML/MTK-style partial-differentiation
operator. Differential(var)(operand) accepts function-form expressions
(returns DerivativeExpr) and bare GiacExpr operands (returns plain GiacExpr
via Commands.diff), matching SymPy.jl's diff(expr, var) and Symbolics.jl's
Differential. Two-argument shorthand Differential(var, n) matches
Symbolics' Differential(x, 2).
- Widen DerivativeExpr internally to steps::Vector{Tuple{String, Int}}.
Adjacent same-variable steps collapse, mixed variables compose freely so
cross/higher-order partials work uniformly.
- Deprecate D: every D(...) call shape now emits Base.depwarn pointing to
Differential. Multi-arg D(f) on a function f(x, y) raises ArgumentError
instead of silently picking the first variable. D removal scheduled for
the next published release.
- Display: derivative orders >= 4 render as f^(n)(x) rather than long prime
strings; DerivativePoint string output keeps prime form (GIAC consumes it
in initial conditions).
- Docs: new migration guide (docs/src/migration/d_to_differential.md);
Differential coverage in mathematics/calculus.md; ODE doc rewritten to
lead with Differential; new Pluto notebook examples/07_odes_pdes.jl with
worked symbolic ODE/PDE walkthroughs; CHANGELOG [Unreleased] entries
under Added / Deprecated / Changed.
- Tests: 9078 passing under Pkg.test() (+91 over baseline), zero failing
regressions. Doc build clean.
Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## main #27 +/- ##
==========================================
+ Coverage 80.64% 81.23% +0.58%
==========================================
Files 24 25 +1
Lines 3018 3112 +94
==========================================
+ Hits 2434 2528 +94
Misses 584 584 ☔ View full report in Codecov by Harness. 🚀 New features to boost your workflow:
|
Collaborator
Author
Contributor
|
@s-celles Seems like a good change to me. SymPy has both |
s-celles
changed the title
…ive display
Multi-step `Base.show` on `DerivativeExpr` previously rendered
`Differential(y)(Differential(x)(f))` as `D: ∂²f/∂x∂y`, which matches the
index/`f_{xy}` convention but conflicts with the operator-product reading
`(∂/∂y)(∂/∂x)f = ∂²f/∂y∂x`. The two conventions are equivalent in value
(Schwarz/Clairaut) but the notational mismatch made the displayed form
look inverted relative to the application order.
Adopt the right-to-left Leibniz convention everywhere user-facing: in
`∂ⁿf/∂v₁…∂vₙ` the rightmost variable is applied first, the leftmost
last. So `Differential(y)(Differential(x)(f))` (apply x first, then y)
now prints as `D: ∂²f/∂y∂x`. The internal `steps` field (innermost-first)
and the GIAC-side `diff(diff(f,x),y)` string are unchanged.
Updates:
- `Base.show(::DerivativeExpr)` iterates `steps` in reverse for the
denominator
- docstrings in `src/differential.jl` and `docs/src/mathematics/calculus.md`
call out the convention explicitly under a new "Notation" section
- migration guide updated; existing `test/test_types.jl` assertions
updated to match the new output; new `test/test_differential.jl`
testset locks the convention with 2- and 3-variable composition cases
- CHANGELOG documents the notation flip under Fixed.
…ives` Round out the `Differential` operator surface to match Symbolics.jl so code written for one runs on the other without rewrites. Operators on `Differential`: - `Differential(t)^n` for `n ≥ 0` — `Differential(t)^2 === Differential(t, 2)` and `Differential(t)^0 === identity`. Negative powers throw `ArgumentError` (anti-derivatives need an explicit constant). - `Differential(y) * Differential(x)` — composition, defined as `Differential(y) ∘ Differential(x)`. Julia's generic `∘` already does the right thing on callables; the explicit `*` method gives uniform delegation and cleaner stack traces. `expand_derivatives`: - `expand_derivatives(d::DerivativeExpr)` forces evaluation by delegating to GIAC's `diff` and returns a plain `GiacExpr`. - `expand_derivatives(x)` is the identity on anything else — so `expand_derivatives(Differential(x)(expr))` written in the Symbolics style runs unchanged on Giac.jl, where the bare-expression branch already evaluates eagerly. Tests cover `^` (n = 0, 1, 2, 3 and same-variable collapse via the existing `_append_step`), `*` and `∘` (cross and same-variable cases), and `expand_derivatives` on `GiacExpr` (identity) and `DerivativeExpr` (forced evaluation, asserting on type + `diff(...)` content rather than exact string since GIAC may renormalize `diff(f(x,y),x)` to its internal `diff(f,0)(x,y)` operator-then-evaluate form). Docs + CHANGELOG updated under Added.
|
Same as @jverzani, this is likely a good change, as it aligns better with other tools. Another possibility could maybe be to keep both |
Two conflicts, both structural rather than semantic. docs/make.jl: main restructured the page list into a `_pages` variable while this branch still edited the inline `pages = [...]`. Took main's file and re-applied this branch's only change to it — the Migration section pointing at docs/src/migration/d_to_differential.md, which is present. Syntax checked. CHANGELOG.md: the conflict hunk spanned past [Unreleased] into the published 0.14.2 block, so a naive resolution would have filed this branch's entries under a released version. Kept everything inside [Unreleased] and consolidated it: main and this branch each carried several sections of the same name, giving duplicate ### Added and ### Fixed headers. Now one section per type in Keep a Changelog order — Added, Changed, Deprecated, Fixed — with all 20 entries preserved (asserted by count, not by eye). Brings in the LibPARI bridge, TermInterface head/children, the STRNG conversion fix, CompatHelper/Dependabot/downgrade CI, macOS aarch64 and the four action bumps.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
4 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.