Re: [boost] Visual Studio 2015 Update 3 has removed std::unary_function and std::binary_function

Subject: Re: [boost] Visual Studio 2015 Update 3 has removed std::unary_function and std::binary_function
From: Marshall Clow (mclow.lists_at_[hidden])
Date: 2016-11-05 22:52:52

On Sat, Nov 5, 2016 at 5:38 PM, Edward Diener <eldiener_at_[hidden]>
wrote:

> On 11/5/2016 3:21 PM, Marshall Clow wrote:
>
>> ... if you build with /std:c++latest.
>>
>> See https://svn.boost.org/trac/boost/ticket/12586 for an example.
>>
>> Other vendors will be removing these types in C++17 mode in the future (or
>> at least requiring a -D RETAIN_REMOVED_STUFF=1 or something like that)
>>
>> A quick grep for these terms found 153 instances of "std::unary_function"
>> and 118 of "std::binary_function" across several libraries, including
>> accumulators, algorithm, config, container, function, gil, graph, icl,
>> mpi,
>> msm, polygon, ptr_container, serialization, smart_ptr, tr1, unordered,
>> utility - and probably others.
>>
>> I think that we ought to have a boost-wide solution for this (i.e,
>> everyone
>> should solve this the same way).
>>
>> I can think of three possibilities:
>> * Deny, deny, deny: Boost doesn't work with C++17.  Not my recommendation.
>> * Since std::unary|binary_function is an empty struct with a set of two
>> (or
>> three) typedefs, just define the typedefs everywhere.
>>
>
> What do you mean by "define the typedefs everywhere" ?
>

Everywhere we derive from std::unary_function or std::binary_function,
manually define "result_type", "first_argument_type", etc.

Like this:

Change:

template<typename T>
struct plus: binary_function<T, T, T>
{
T operator() (const T& x, const T& y) { return x + y }
};

to:

  template<typename T>
struct plus
{
typedef T first_argument_type;
typedef T second_argument_type;
typedef T result_type;
T operator() (const T& x, const T& y) { return x + y }
};

-- Marshall