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### 781. `std::complex` should add missing C99 functions

Section: 28.4.7 [complex.value.ops] Status: CD1 Submitter: Daniel Krügler Opened: 2008-01-26 Last modified: 2016-01-28

Priority: Not Prioritized

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Discussion:

A comparision of the N2461 header `<complex>` synopsis ([complex.syn]) with the C99 standard (ISO 9899, 2nd edition and the two corrigenda) show some complex functions that are missing in C++. These are:

1. 7.3.9.4: (required elements of the C99 library)
   The `cproj` functions
2. 7.26.1: (optional elements of the C99 library)

       cerf    cerfc    cexp2
       cexpm1  clog10   clog1p
       clog2   clgamma  ctgamma

I propose that at least the required `cproj` overloads are provided as equivalent C++ functions. This addition is easy to do in one sentence (delegation to C99 function).

Please note also that the current entry `polar` in 28.4.9 [cmplx.over] p. 1 should be removed from the mentioned overload list. It does not make sense to require that a function already expecting scalar arguments should cast these arguments into corresponding `complex<T>` arguments, which are not accepted by this function.

Proposed resolution:

In 28.4.2 [complex.syn] add just between the declaration of `conj` and `fabs`:

>     template<class T> complex<T> conj(const complex<T>&);
>     template<class T> complex<T> proj(const complex<T>&);
>     template<class T> complex<T> fabs(const complex<T>&);

In 28.4.7 [complex.value.ops] just after p.6 (return clause of `conj`) add:

>     template<class T> complex<T> proj(const complex<T>& x);

> > Effects: Behaves the same as C99 function `cproj`, defined in subclause 7.3.9.4."

In 28.4.9 [cmplx.over] p. 1, add one further entry `proj` to the overload list.

> The following function templates shall have additional overloads:

> >     arg           norm
> >     conj          polar proj
> >     imag          real