Is there a difference

[Lu Bu]

Is there a difference declaring a function like this:

int exampleFunction() { return value;}

or like this:

const int exampleFunction() { return value;}

I mean i understand the difference if theres an ampersand sign:

const int& exampleFunction() { return value;}

But what is the difference between the 2 first ones?

[ResidentBiscuit]

int exampleFunction() { return value;} Returns a copy of value

const int exampleFunction() { return value;} Returns a const copy of value

const int& exampleFunction() { return value;} Returns a const reference to value

The difference between the first two: The first one returns a regular copy. Do whatever you want with it. The second returns a const copy, so you can't change value at all. In practice, I don't think I've ever seen the second example. Code will almost always return a copy, a reference, or a const reference.

EDIT: See this thread for thread for some discussion http://stackoverflow.com/q/8716330/2887128

[Yay295]

I suppose a compiler might be able to make some optimizations with the second example? If not, I don't see how it could be useful.

[Cubbi]

The word "const" in "const int exampleFunction()" has no meaning. There is no difference between #1 and #2. Compilers will warn:

test.cc:6:1: warning: 'const' type qualifier on return type has no effect [-Wignored-qualifiers]
const int exampleFunction() { return value;}
^~~~~~
1 warning generated.

test.cc:6:27: warning: type qualifiers ignored on function return type [-Wignored-qualifiers]

test.cc(6): warning #858: type qualifier on return type is meaningless
  const int exampleFunction() { return value;}
  ^

(note, if you return a class type (class/struct/union), then const is meaningful)