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Asked: 2026-06-15T08:34:57+00:00

I was reviewing some code and came upon a line similar to: std::tr1::function<bool (int,

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I was reviewing some code and came upon a line similar to:

std::tr1::function<bool (int, int)>(//etc...

The syntax for the template type, bool (int, int) was unfamiliar to me. Based on Googling, in the case of std::tr1::function it seems this syntax is used to define a function’s return type and parameters. That makes sense, but why does that syntax work? As far as I know, C++ templates can only specify types?

I tried to instantiate an instance of the type in code as:

bool (int, int) test;

As I expected, the statement failed to compile. At the very least, the syntax would need to be something like:
bool (test)(int, int);

Is bool (int, int) treated as a C++ type? Any tips on reconciling this in my mind?

Thanks,
Adam

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1 Answer

  1. Editorial Team

    It is called a function type.

    You can’t create instances of it, but you can create pointers to them and typedefs.

    This question has some insight: What is a function type used for?

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