Function

Argument Passing

By default, arguments are pass by value copying the input to the argument varaible.

Pass by Reference

To not copy the input, use pass-by-reference by modifying the argument to be &arg.

void f(vector<int> &v) {

}

Immutable

If an argument is mutable but you’d like to indicate that it should be immutable inside the function/local scope, you can modify the argument to be const arg.

It is very common to see const applied to pass-by-reference rather than pass-by-value.

Return Value

By default, object are return-by-value meaning the object return are copied.

vector copy(const vector<int> &v) {
	vector p;

	for (i=1; i < sizeof(v); ++i) {
		p[i] = &v[i];
	}

	return p;
}

Return by Pointer

This is not recommended. To prevent return-by-value, one may have the pointer return instead:

vector* copy(const vector<int> &v) {
	vector* p = new vector;

	for (i=1; i < sizeof(v); ++i) {
		p[i] = &v[i];
	}

	return p;
}

Return by Reference

Never do this! The reference will point to nonsense because the local scope may disappear.

vector& copy(const vector<int> &v) {
	vector rv = new vector;

	for (i=1; i < sizeof(v); ++i) {
		p[i] = &v[i];
	}

	return rv;
}