[c++] Passing an array by reference

It's a syntax for array references - you need to use (&array) to clarify to the compiler that you want a reference to an array, rather than the (invalid) array of references int & array[100];.

EDIT: Some clarification.

void foo(int * x);
void foo(int x[100]);
void foo(int x[]);

These three are different ways of declaring the same function. They're all treated as taking an int * parameter, you can pass any size array to them.

void foo(int (&x)[100]);

This only accepts arrays of 100 integers. You can safely use sizeof on x

void foo(int & x[100]); // error

This is parsed as an "array of references" - which isn't legal.