Can I use non-default datatype as argument for functions in 1 line?

Question

I think the title of question is little bit confusing, so I'll explain that.

Let's see this very simple code.

#include <iostream>

class C {
public:
    int val;

    C(){
        val = 2;
    }

    void changeVal(int i){
        val = i;
    }

};

void printout(int val){
    std::cout << "int val : " << val << std::endl;
}

void printout(C c){
    std::cout << "class val : " << c.val << std::endl;
}

int main()
{
    C c;
    printout(1);
    printout(c);    

    //printout(C());    // ok, I can understand it.
    //printout(C().changeVal(0)); /// ?????
    return 0;
}

As you can see, function 'printout' is for printing out the input argument. My question is, when I use the int value(default datatype), then I just put in the function real number '1', however, when I use my class instance('class C'), then I have to declare my class instance before the function.

So, is there any way to make this kind of non-default datatype for function argument in 1-line?

The actual situation is, I have to use the 4x4 matrix as argument for some function. For this reason, I have to make some matrix, and initialize(make zero) that, and use it. But if I can do this same job with just 1 line, my source code will be more clear than now.

That's my question. I hope you could understand my question. Thank you.

I've removed the C tag. The use of class and <iostream> implies that this question is about C++ only — simonc
– simonc, Commented Aug 22, 2013 at 6:36
Btw not sure what you mean by "Default datatype", "built in language datatype/primitive type" would be better — Karthik T
– Karthik T, Commented Aug 22, 2013 at 6:40
@simonc Thank you for your guide. I'm not familiar this system — CIMPLE
– CIMPLE, Commented Aug 22, 2013 at 6:47
@KarthikT Oh, that kinds of representation is much better. Thank you. — CIMPLE
– CIMPLE, Commented Aug 22, 2013 at 6:51

juanchopanza · Accepted Answer · 2013-08-22 06:38:13Z

2

You can pass a temporary:

printout(C());

Note that, since you don't need a copy of the C parameter, it would make more sense to pass it by const reference:

void printout(const C& c) { ... }

answered Aug 22, 2013 at 6:38

juanchopanza

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3 Comments

CIMPLE Over a year ago

Thank you for your answer. Then I want to ask one more question. Can I use my member function for initialization with similar way?

CIMPLE Over a year ago

I added 'changeVal' function. I want to initialize my member variable 'val' as 0, then I'll use 'changeVal' function for that. Can I do this job in 1 line for function argument?

juanchopanza Over a year ago

@CIMPLE if you want to initialize val to 0, you don't need to call changeVal. You can write the default constructor like this: C() : val(0) {} or even C() : val() {}.

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