Int Argument in operator++
class myClass
{
public:
void operator++()
{
// ++myInstance.
}
开发者_JAVA百科 void operator++(int)
{
// myInstance++.
}
}
Besides letting the compiler distinguish between myInstance++
and ++myInstance
, is the optional int
argument in operator++
actually for anything? If so, what is it?
As @Konrad said, the int argument is not used for anything, other than to distingush between the pre-increment and post-increment forms.
Note however that your operators should return a value. Pre-increment should return a reference, and post-increment should return by-value. To wit:
class myClass
{
public:
myClass& operator++()
{
// ++myInstance.
return * this;
}
myClass operator++(int)
{
// myInstance++.
myClass orig = *this;
++(*this); // do the actual increment
return orig;
}
};
EDIT:
As Gene Bushuyev mentions correctly below, it is not an absolute requirement that operator++
return non-void. However, in most cases (I can't think of an exception) you'll need to. Especially if you want to assign the results of the operator to some other value, such as:
myClass a;
myClass x = a++;
EDIT2:
Also, with the postimcrement version, you will return the object before it was incremented. This is typically done using a local temporary. See above.
is the optional int argument in operator++ actually for anything?
No. The only purpose is to distinguish between the two overloads. Quite disappointing, I know. ;-)
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