Function with a size_t Template Parameter

Question

I'm trying to understand the template function. The ultimate goal is to pass an entire array to a function. There seem to be many different ways to implement this but they all use the template function. Here's one of the simpler examples I've found...

template<size_t N>
void h(Sample (&arr)[N])
{
    size_t count = N; //N is 10, so would be count!
    //you can even do this now:
    //size_t count = sizeof(arr)/sizeof(arr[0]);  it'll return 10!
}
Sample arr[10];
h(arr); //pass : same as before!

I thought template<> was used to create a variable that could be used in place of int, float, char, etc.. what's the point of specifying the type (size_t), what does this do?

See [non-type template parameters](http://en.cppreference.com/w/cpp/language/template_parameters#Template_non-type_arguments). — Ami Tavory, Jan 23 '16 at 20:41
"The ultimate goal is to pass an entire array to a function". Use std::array or std::vector. — n. m. could be an AI, Apr 25 '18 at 10:04
@n.m. passing a `std::array` likely still needs the function to templated on the array length - so the question stays relevant even with that fix. — Toby Speight, Apr 25 '18 at 10:12

score 3 · Answer 1 · edited Apr 25 '18 at 10:13

3

The size_t N template parameter is a deduced integral value based upon the array size passed to the template function. Templates parameters can be

non-type template parameter;
type template parameter;
template template parameter.

Reference: Template Parameters.

edited Apr 25 '18 at 10:13

Toby Speight

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answered Jan 23 '16 at 20:31

ThomasMcLeod

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score -1 · Answer 2 · answered Jan 23 '16 at 20:55

-1

You can reuse the template for arrays of any size.

answered Jan 23 '16 at 20:55

Bartosz Bosowiec

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Function with a size_t Template Parameter

2 Answers2