Issue #19543: Implementation of isclose as per PEP 485
For details, see:
PEP 0485 -- A Function for testing approximate equality
Functions added: math.isclose() and cmath.isclose().
Original code by Chris Barker. Patch by Tal Einat.
diff --git a/Modules/cmathmodule.c b/Modules/cmathmodule.c
index 921eaaa..d12e4c5 100644
--- a/Modules/cmathmodule.c
+++ b/Modules/cmathmodule.c
@@ -1114,6 +1114,73 @@
Py_IS_INFINITY(z.imag));
}
+/*[clinic input]
+cmath.isclose -> bool
+
+ a: Py_complex
+ b: Py_complex
+ *
+ rel_tol: double = 1e-09
+ maximum difference for being considered "close", relative to the
+ magnitude of the input values
+ abs_tol: double = 0.0
+ maximum difference for being considered "close", regardless of the
+ magnitude of the input values
+
+Determine whether two complex numbers are close in value.
+
+Return True if a is close in value to b, and False otherwise.
+
+For the values to be considered close, the difference between them must be
+smaller than at least one of the tolerances.
+
+-inf, inf and NaN behave similarly to the IEEE 754 Standard. That is, NaN is
+not close to anything, even itself. inf and -inf are only close to themselves.
+[clinic start generated code]*/
+
+static int
+cmath_isclose_impl(PyModuleDef *module, Py_complex a, Py_complex b,
+ double rel_tol, double abs_tol)
+/*[clinic end generated code: output=da0c535fb54e2310 input=df9636d7de1d4ac3]*/
+{
+ double diff;
+
+ /* sanity check on the inputs */
+ if (rel_tol < 0.0 || abs_tol < 0.0 ) {
+ PyErr_SetString(PyExc_ValueError,
+ "tolerances must be non-negative");
+ return -1;
+ }
+
+ if ( (a.real == b.real) && (a.imag == b.imag) ) {
+ /* short circuit exact equality -- needed to catch two infinities of
+ the same sign. And perhaps speeds things up a bit sometimes.
+ */
+ return 1;
+ }
+
+ /* This catches the case of two infinities of opposite sign, or
+ one infinity and one finite number. Two infinities of opposite
+ sign would otherwise have an infinite relative tolerance.
+ Two infinities of the same sign are caught by the equality check
+ above.
+ */
+
+ if (Py_IS_INFINITY(a.real) || Py_IS_INFINITY(a.imag) ||
+ Py_IS_INFINITY(b.real) || Py_IS_INFINITY(b.imag)) {
+ return 0;
+ }
+
+ /* now do the regular computation
+ this is essentially the "weak" test from the Boost library
+ */
+
+ diff = _Py_c_abs(_Py_c_diff(a, b));
+
+ return (((diff <= rel_tol * _Py_c_abs(b)) ||
+ (diff <= rel_tol * _Py_c_abs(a))) ||
+ (diff <= abs_tol));
+}
PyDoc_STRVAR(module_doc,
"This module is always available. It provides access to mathematical\n"
@@ -1129,6 +1196,7 @@
CMATH_COS_METHODDEF
CMATH_COSH_METHODDEF
CMATH_EXP_METHODDEF
+ CMATH_ISCLOSE_METHODDEF
CMATH_ISFINITE_METHODDEF
CMATH_ISINF_METHODDEF
CMATH_ISNAN_METHODDEF