Patch #1675423: PyComplex_AsCComplex() now tries to convert an object

to complex using its __complex__() method before falling back to the
__float__() method. Therefore, the functions in the cmath module now
can operate on objects that define a __complex__() method.
 (backport)

2 files changed, 16 insertions, 4 deletions

diff --git a/Doc/api/concrete.tex b/Doc/api/concrete.tex
index e2d3e52..3b2945e 100644
--- a/Doc/api/concrete.tex
+++ b/Doc/api/concrete.tex
@@ -443,7 +443,9 @@ booleans.  The following macros are available, however.
 
 \begin{cfuncdesc}{double}{PyFloat_AsDouble}{PyObject *pyfloat}
   Return a C \ctype{double} representation of the contents of
-  \var{pyfloat}.
+  \var{pyfloat}.  If \var{pyfloat} is not a Python floating point
+  object but has a \method{__float__} method, this method will first
+  be called to convert \var{pyfloat} into a float.
 \end{cfuncdesc}
 
 \begin{cfuncdesc}{double}{PyFloat_AS_DOUBLE}{PyObject *pyfloat}
@@ -558,8 +560,11 @@ typedef struct {
 \end{cfuncdesc}
 
 \begin{cfuncdesc}{Py_complex}{PyComplex_AsCComplex}{PyObject *op}
-  Return the \ctype{Py_complex} value of the complex number
-  \var{op}.
+  Return the \ctype{Py_complex} value of the complex number \var{op}.
+  \versionchanged[If \var{op} is not a Python complex number object
+                  but has a \method{__complex__} method, this method
+		  will first be called to convert \var{op} to a Python
+		  complex number object]{2.6}
 \end{cfuncdesc}
 
 
diff --git a/Doc/lib/libcmath.tex b/Doc/lib/libcmath.tex
index 54e0cdb..f8aa45b 100644
--- a/Doc/lib/libcmath.tex
+++ b/Doc/lib/libcmath.tex
@@ -5,7 +5,14 @@
 \modulesynopsis{Mathematical functions for complex numbers.}
 
 This module is always available.  It provides access to mathematical
-functions for complex numbers.  The functions are:
+functions for complex numbers.  The functions in this module accept
+integers, floating-point numbers or complex numbers as arguments.
+They will also accept any Python object that has either a
+\method{__complex__} or a \method{__float__} method: these methods are
+used to convert the object to a complex or floating-point number, respectively, and
+the function is then applied to the result of the conversion.
+
+The functions are:
 
 \begin{funcdesc}{acos}{x}
 Return the arc cosine of \var{x}.