CODEWITHSUNDEEP
c++templatesc-preprocessordry
Nick
Nick

Reputation: 10539

C++ templates and C preprocessor

Consider for a moment this code. Is not important what the code do, but how template boilerplate code is written.

From boilerplate point of view, the code has some important advantages.

Disadvantages are obvious:

Is there anything standardized like this?

#include <cstdio>

template<typename T>
struct Summator{
    Summator(T v1, T v2);

    T value1();
    T value2();

    T sum();

    bool great();

private:
    T v1;
    T v2;
};


#define Summator_(type) template<typename T> type Summator<T>


Summator_()::Summator(T v1, T v2) : v1(v1), v2(v2){};

Summator_(T)::value1(){
    return v1;
}

Summator_(T)::value2(){
    return v1;
}

Summator_(T)::sum(){
    return v1 + v2;
}

Summator_(bool)::great(){
    return v1 > v2;
}

int main(){
    Summator<int> s{ 5, 6 };

    printf("%d\n", s.sum() );
}

Upvotes: 3

Views: 1456

Answers (3)

Richard Hodges
Richard Hodges

Reputation: 69864

much less boilerplate code.

No, it's the same

if you decide to take more template parameters, you change only class definition and the #define.

read: if you decide to completely change the design... maybe you might save some typing (but then again, maybe not)

using preprocessor

Yup - so that's a no right there.

not so readable

so "no" again

just weird

irrelevant

Is there anything standardized like this?

clearly not

Upvotes: 0

Pieter
Pieter

Reputation: 17705

If I understand your question correctly you want to avoid to have to write the whole template in front of every function definition?

I think most people who care about this rely on an IDE to generate empty function definitions / refactor existing functions?

I don't think using macro's is a good idea for this, just to save a little typing, feels like a maintenance nightmare in the making.

Upvotes: 1

Martin Bonner supports Monica
Martin Bonner supports Monica

Reputation: 28987

Given that for most practical purposes, member functions of class templates have to be inline, you might as well define them in the body of the calls. Particularly for tiny functions like this.

Obviously real class templates are likely to have one or two non-trivial functions - but then you only need the boiler plate for those one or two functions.

There is nothing defined in the standard to help with this, and I'm not sure I'd want there to be. If you must do it, remember to #undef the define afterwards (because otherwise you will pollute the #define namespace of the user of your class).

Upvotes: 1

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