Add promote_symtype for ComposedFunction (fixes #650)#859
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AayushSabharwal merged 2 commits intoJuliaSymbolics:masterfrom Feb 27, 2026
Merged
Add promote_symtype for ComposedFunction (fixes #650)#859AayushSabharwal merged 2 commits intoJuliaSymbolics:masterfrom
AayushSabharwal merged 2 commits intoJuliaSymbolics:masterfrom
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Thanks for the contribution! Your tests look pretty good. However, some changes are necessary here. I've outlined them below. Once they're addressed, please feel free to ping me again for a review.
src/methods.jl
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| """ | ||
| function promote_symtype(f::Base.ComposedFunction, arg_symtypes...) | ||
| # Unwrap the composition into a vector [innermost, ..., outermost] | ||
| funcs = Base.unwrap_composed(f) |
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Base.unwrap_composed is internal. This approach also makes every subsequent promote_symtype in this function a dynamic dispatch, since Julia cannot infer the type of each element in funcs. ComposedFunction documents its fields: the wrapped functions can be obtained as .inner and .outer. A better approach would be to call promote_symtype on .inner with arg_symtypes, and pass the result of that to promote_symtype on .outer.
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Done
src/methods.jl
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| the argument to the next function. Multi-argument returns (tuples) are not | ||
| currently supported but could be added if needed. | ||
| """ | ||
| function promote_symtype(f::Base.ComposedFunction, arg_symtypes...) |
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Suggested change
| function promote_symtype(f::Base.ComposedFunction, arg_symtypes...) | |
| function promote_symtype(f::Base.ComposedFunction, arg_symtypes::TypeT...) |
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Done
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Changes implemented as suggested . Replaced Base.unwrap_composed with the recursive .inner/.outer approach. |
AayushSabharwal
merged commit 540c557
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JuliaSymbolics:master
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Summary
Adds
promote_symtypesupport for composed functions (e.g.,sin ∘ sqrt).Problem
When you compose functions with
∘, SymbolicUtils doesn't know how to infer the result type, so it returnsAnyinstead of the actual type.Solution
Unwrap the composition and fold type information from inner to outer function.
Before:
After:
Testing
Added tests for 2, 3, and 4-function compositions with different input types. All pass.
Closes #650