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: Josh Juran (jjuran_at_[hidden])
Date: 2016-11-05 18:01:51

On Nov 5, 2016, at 5:01 PM, Andrey Semashev <andrey.semashev_at_[hidden]> wrote:

> On 11/05/16 22:21, Marshall Clow wrote:
> 
>> Other vendors will be removing these types in C++17 mode in the future
>> 
>> A quick grep for these terms found 153 instances of "std::unary_function"
>> and 118 of "std::binary_function" across several libraries
>> 
>> 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.  Note that the
>> typedefs (result_type, first_argument_type, second_argument_type) were
>> deemed to not be useful in C++17 due to the existence of advanced type
>> traits, etc.
>> * Define a boost:unary_function and boost::binary_function struct that
>> mimics the one that was in namespace std, and change over to use that.
>> * Something else.
>> 
>> Comments?

#1 is obviously a non-starter.  #3 requires changing the same number of use sites as #2, with the minor one-time advantage of requiring only a trivial search/replace operation, but at the cost of adding a new component.

> I'm in favor of replacing the structs with typedefs (i.e. option #2).

I agree.  I did this some time ago to my own code (to reduce the length of translation units by not including <functional>) and found the result more readable.

Josh