I am confused that why following code is not able to compile
int foo(const float* &a) {
return 0;
}
int main() {
float* a;
foo(a);
return 0;
}
Compiler give error as:
error: invalid initialization of reference of type 'const float*&' from expression of type 'float*'
but when I try to pass without by reference in foo, it is compiling fine.
I think it should show same behavior whether I pass by reference or not.
Thanks,
Because it isn't type-safe. Consider:
const float f = 2.0;
int foo(const float* &a) {
a = &f;
return 0;
}
int main() {
float* a;
foo(a);
*a = 7.0;
return 0;
}
Any non-const
reference or pointer must necessarily be invariant in the pointed-to type, because a non-const
pointer or reference supports reading (a covariant operation) and also writing (a contravariant operation).
const
must be added from the greatest indirection level first. This would work:
int foo(float* const &a) {
return 0;
}
int main() {
float* a;
foo(a);
return 0;
}