GH-50197: [C++][Python] Add "hypot" compute kernel#50198
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Add a binary floating-point compute function "hypot" that computes the hypotenuse sqrt(x^2 + y^2) without undue overflow or underflow at intermediate stages, mirroring numpy.hypot and std::hypot. The kernel reuses the existing MakeArithmeticFunctionFloatingPoint factory (as atan2 does), registering float32 and float64 kernels and promoting integer/decimal inputs to float64 via DispatchBest. Also adds the Hypot() convenience function and declaration, a FunctionDoc, C++ tests (including an overflow-safety test that exercises inputs whose squares overflow float32), a compute.rst entry, and pyarrow expression coverage.
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Rationale for this change
Arrow has
atan2andlogbbut nohypot. Computing a Euclidean norm currently needssqrt(add(multiply(x, x), multiply(y, y))), which can overflow at themultiplystep even when the result is representable.What changes are included in this PR?
Add a
hypotkernel backed bystd::hypot(float32/float64, with integer/decimal inputs promoted to float64), theHypot()C++ function, aFunctionDocandcompute.rstentry, and a Python expression test.pc.hypotis auto-exposed from the registry.Are these changes tested?
Yes, C++ tests for the basic cases, null/NaN/Inf handling, and an overflow case confirming it doesn't fall back to a naive
sqrt(x*x + y*y).Are there any user-facing changes?
Yes, a new
hypotfunction in C++ and Python. Additive only.