add C++ declarations for std::complex type (proposed by Nick Foti)

Cython/Includes/libcpp/complex.pxd

+# Note: add integer versions of the functions?
+
+cdef extern from "<complex>" namespace "std" nogil:
+    cdef cppclass complex[T]:
+        complex() except +
+        complex(T, T) except +
+        complex(complex[T]&) except +
+        # How to make the converting constructor, i.e. convert complex[double]
+        # to complex[float]?
+
+        complex[T] operator+(complex[T]&)
+        complex[T] operator-(complex[T]&)
+        complex[T] operator+(complex[T]&, complex[T]&)
+        complex[T] operator+(complex[T]&, T&)
+        complex[T] operator+(T&, complex[T]&)
+        complex[T] operator-(complex[T]&, complex[T]&)
+        complex[T] operator-(complex[T]&, T&)
+        complex[T] operator-(T&, complex[T]&)
+        complex[T] operator*(complex[T]&, complex[T]&)
+        complex[T] operator*(complex[T]&, T&)
+        complex[T] operator*(T&, complex[T]&)
+        complex[T] operator/(complex[T]&, complex[T]&)
+        complex[T] operator/(complex[T]&, T&)
+        complex[T] operator/(T&, complex[T]&)
+
+        bint operator==(complex[T]&, complex[T]&)
+        bint operator==(complex[T]&, T&)
+        bint operator==(T&, complex[T]&)
+        bint operator!=(complex[T]&, complex[T]&)
+        bint operator!=(complex[T]&, T&)
+        bint operator!=(T&, complex[T]&)
+
+        # Access real part
+        T real()
+        void real(T)
+
+        # Access imaginary part
+        T image()
+        void image(T)
+
+    # Return real part
+    T real(complex[T]&)
+    long double real(long double)
+    double real(double)
+    float real(float)
+
+    # Return imaginary part
+    T imag(complex[T]&)
+    long double imag(long double)
+    double imag(double)
+    float imag(float)
+
+    T abs(complex[T]&)
+    T arg(complex[T]&)
+    long double arg(long double)
+    double arg(double)
+    float arg(float)
+
+    T norm(complex[T])
+    long double norm(long double)
+    double norm(double)
+    float norm(float)
+
+    complex[T] conj(complex[T]&)
+    complex[long double] conj(long double)
+    complex[double] conj(double)
+    complex[float] conj(float)
+
+    complex[T] proj(complex[T])
+    complex[long double] proj(long double)
+    complex[double] proj(double)
+    complex[float] proj(float)
+
+    complex[T] polar(T&, T&)
+    complex[T] ploar(T&)
+
+    complex[T] exp(complex[T]&)
+    complex[T] log(complex[T]&)
+    complex[T] log10(complex[T]&)
+
+    complex[T] pow(complex[T]&, complex[T]&)
+    complex[T] pow(complex[T]&, T&)
+    complex[T] pow(T&, complex[T]&)
+    # There are some promotion versions too
+
+    complex[T] sqrt(complex[T]&)
+
+    complex[T] sin(complex[T]&)
+    complex[T] cos(complex[T]&)
+    complex[T] tan(complex[T]&)
+    complex[T] asin(complex[T]&)
+    complex[T] acos(complex[T]&)
+    complex[T] atan(complex[T]&)
+
+    complex[T] sinh(complex[T]&)
+    complex[T] cosh(complex[T]&)
+    complex[T] tanh(complex[T]&)
+
+    complex[T] asinh(complex[T]&)
+    complex[T] acosh(complex[T]&)
+    complex[T] atanh(complex[T]&)