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3074. Non-member functions forvalarray should only deduce from thevalarray

Section: 29.6.3[valarray.nonmembers]Status:C++20Submitter: Jonathan WakelyOpened: 2018-02-28Last modified: 2021-02-25

Priority:0

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Discussion:

The expression(std::valarray<double>{} * 2) is ill-formed, because argument deduction fails for:

template<class T>  valarray<T> operator*(const valarray<T>&, const T&);

Is there any reason to try and deduce the argument from the scalar, instead of only deducing from the valarray and allowing implicit conversions to the scalar? i.e.

template<class T>   valarray<T> operator*(const valarray<T>&, const typename valarray<T>::value_type&);

[2018-03-07 Moved to Tentatively Ready after 5 positive votes on c++std-lib.]

[2018-06 Rapperswil: Adopted]

Proposed resolution:

This wording is relative toN4727.

1. Edit 29.6.1[valarray.syn], header<valarray> synopsis, as indicated:

   […]template<class T> valarray<T> operator* (const valarray<T>&, const valarray<T>&);template<class T> valarray<T> operator* (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator* (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator/ (const valarray<T>&, const valarray<T>&);template<class T> valarray<T> operator/ (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator/ (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator% (const valarray<T>&, const valarray<T>&);template<class T> valarray<T> operator% (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator% (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator+ (const valarray<T>&, const valarray<T>&);template<class T> valarray<T> operator+ (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator+ (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator- (const valarray<T>&, const valarray<T>&);template<class T> valarray<T> operator- (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator- (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator^ (const valarray<T>&, const valarray<T>&);template<class T> valarray<T> operator^ (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator^ (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator& (const valarray<T>&, const valarray<T>&);template<class T> valarray<T> operator& (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator& (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator| (const valarray<T>&, const valarray<T>&);template<class T> valarray<T> operator| (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator| (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator<<(const valarray<T>&, const valarray<T>&);template<class T> valarray<T> operator<<(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator<<(constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator>>(const valarray<T>&, const valarray<T>&);template<class T> valarray<T> operator>>(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator>>(constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<bool> operator&&(const valarray<T>&, const valarray<T>&);template<class T> valarray<bool> operator&&(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<bool> operator&&(constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<bool> operator||(const valarray<T>&, const valarray<T>&);template<class T> valarray<bool> operator||(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<bool> operator||(constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<bool> operator==(const valarray<T>&, const valarray<T>&);template<class T> valarray<bool> operator==(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<bool> operator==(constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<bool> operator!=(const valarray<T>&, const valarray<T>&);template<class T> valarray<bool> operator!=(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<bool> operator!=(constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<bool> operator< (const valarray<T>&, const valarray<T>&);template<class T> valarray<bool> operator< (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<bool> operator< (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<bool> operator> (const valarray<T>&, const valarray<T>&);template<class T> valarray<bool> operator> (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<bool> operator> (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<bool> operator<=(const valarray<T>&, const valarray<T>&);template<class T> valarray<bool> operator<=(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<bool> operator<=(constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<bool> operator>=(const valarray<T>&, const valarray<T>&);template<class T> valarray<bool> operator>=(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<bool> operator>=(constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> abs (const valarray<T>&);template<class T> valarray<T> acos (const valarray<T>&);template<class T> valarray<T> asin (const valarray<T>&);template<class T> valarray<T> atan (const valarray<T>&);template<class T> valarray<T> atan2(const valarray<T>&, const valarray<T>&);template<class T> valarray<T> atan2(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> atan2(constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> cos (const valarray<T>&);template<class T> valarray<T> cosh (const valarray<T>&);template<class T> valarray<T> exp (const valarray<T>&);template<class T> valarray<T> log (const valarray<T>&);template<class T> valarray<T> log10(const valarray<T>&);template<class T> valarray<T> pow(const valarray<T>&, const valarray<T>&);template<class T> valarray<T> pow(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> pow(constTtypename valarray<T>::value_type&, const valarray<T>&);[…]

2. Edit 29.6.3.1[valarray.binary] as indicated:

   […]template<class T> valarray<T> operator* (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator* (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator/ (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator/ (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator% (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator% (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator+ (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator+ (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator- (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator- (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator^ (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator^ (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator& (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator& (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator| (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator| (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator<<(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator<<(constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> operator>>(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> operator>>(constTtypename valarray<T>::value_type&, const valarray<T>&);[…]

3. Edit 29.6.3.2[valarray.comparison] as indicated:

   […]template<class T> valarray<bool> operator==(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<bool> operator==(constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<bool> operator!=(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<bool> operator!=(constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<bool> operator< (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<bool> operator< (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<bool> operator> (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<bool> operator> (constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<bool> operator<=(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<bool> operator<=(constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<bool> operator>=(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<bool> operator>=(constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<bool> operator&&(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<bool> operator&&(constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<bool> operator||(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<bool> operator||(constTtypename valarray<T>::value_type&, const valarray<T>&);[…]

4. Edit 29.6.3.3[valarray.transcend] as indicated:

   template<class T> valarray<T> abs (const valarray<T>&);template<class T> valarray<T> acos (const valarray<T>&);template<class T> valarray<T> asin (const valarray<T>&);template<class T> valarray<T> atan (const valarray<T>&);template<class T> valarray<T> atan2(const valarray<T>&, const valarray<T>&);template<class T> valarray<T> atan2(const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> atan2(constTtypename valarray<T>::value_type&, const valarray<T>&);template<class T> valarray<T> cos (const valarray<T>&);template<class T> valarray<T> cosh (const valarray<T>&);template<class T> valarray<T> exp (const valarray<T>&);template<class T> valarray<T> log (const valarray<T>&);template<class T> valarray<T> log10(const valarray<T>&);template<class T> valarray<T> pow (const valarray<T>&, const valarray<T>&);template<class T> valarray<T> pow (const valarray<T>&, constTtypename valarray<T>::value_type&);template<class T> valarray<T> pow (constTtypename valarray<T>::value_type&, const valarray<T>&);[…]