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Editorial Team
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Asked: 2026-05-26T12:59:10+00:00

I was researching what std::bind is and what it’s for (that may eventually be

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I was researching what std::bind is and what it’s for (that may eventually be a different question) at MSDN: http://msdn.microsoft.com/en-us/library/bb982702.aspx

And saw that the prototypes listed are: 

template<class Fty, class T1, class T2, ..., class TN>
   unspecified bind(Fty fn, T1 t1, T2 t2, ..., TN tN);
template<class Ret, class Fty, class T1, class T2, ..., class TN>
   unspecified bind(Fty fn, T1 t1, T2 t2, ..., TN tN);

Which confuses me for two reasons. 1) Last I checked, MSVC didn’t implement variadic templates, and 2) My question: what does the word unspecified mean there? (It doesn’t seem related to unspecified behavior.)

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1 Answer

  1. Editorial Team

    The unspecified in the return type means that it is a type that is, well, unspecified. The standard does not require a particular type to be returned from bind, as long as the returned type complies with the requirements that the standard mandates.

    As of the ..., I don’t know whether VS implements them or not, but you will see the same documentation for boost::bind, and it has been compiling in different compilers without variadic template support for some time already… the documentation states that you can pass N arguments of different types, but that does not necessarily mean that there is a single template that does it, it can be implemented in terms of a set of 1-ary, 2-ary… N-ary templates.

    The documentation is showing the behavior that you can expect from using it, rather than the detail of how it is implemented.

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