Don't understand this template with nontype in the book

[yungman]

This is actually very simple. I think the normal way is done like this:

#include<iostream>
using namespace std;
template<class T2>
auto inRange(const T2& value, int low, int hi)
{
    if ((value <= hi) && (value >= low)) return "It is in range.";
    else return " It is out of range.";
}
int main()
{
    int val1 = 99;
    count << inRange(val1, 100, 500)  << "\n\n";
    return 0;
}

But this is from the Ivor book:

#include<iostream>
using namespace std;
template<class T1, int low, int hi>//how does this work
auto inRange(const T1& value)
{
    if ((value <= hi) && (value >= low)) return "It is in range.";
    else return " It is out of range.";
}
int main()
{
    int val2 = 200;
    count << inRange<double, 100, 500>(val2);//what is this, it not in the function parameter
    count << "\n\n";
    return 0;
}

I have no idea what the book is doing, what is inRange<double, 100, 500>(val2);? I never seen this before. Is this something newer than my old Gaddis book again?

Thanks

 

[Mark44]

I have no idea what the book is doing, what is inRange<double, 100, 500>(val2);? I never seen this before. Is this something newer than my old Gaddis book again?

Did you try a web search for "function template instantiation" or similar? I don't believe this is newer than what is presented in the Gaddis book, but his intent wasn't to present every possible detail of all of the features of C++.
Here is some documentation similar to the example you posted - Explicit Instantiation | Microsoft Docs

 

[Filip Larsen]

The std::array we got with C++11 is a very useful example of this.

 

[yungman]

Did you try a web search for "function template instantiation" or similar? I don't believe this is newer than what is presented in the Gaddis book, but his intent wasn't to present every possible detail of all of the features of C++.
Here is some documentation similar to the example you posted - Explicit Instantiation | Microsoft Docs

Yes, I tried. It would really help IF I know to look for Explict Instantiation. Problem for me is if I don't know the syntax, I don't know what terms to search.

Honestly, I read your link, I have no idea what it is saying. But now I know the term to look for, I'll dig around.

thanks

 

[Mark44]

It would really help IF I know to look for Explict Instantiation.

This is something that was covered in previous posts about template functions - explicit instantiation vs. implicit instantiation.

Honestly, I read your link, I have no idea what it is saying.

Well, that's a problem. You can't get very far in programming if you don't understand what is being said in the documentation for some feature of the language.