Execution Context

There are two types of variables in Squirrel, local variables and tables/arrays slots. Because global variables are stored in a table, they are table slots.

A single identifier refers to a local variable or a slot in the environment object.

derefexp := id;

_table["foo"]
_array[10]

with tables we can also use the '.' syntax

derefexp := exp '.' id

_table.foo

Squirrel first checks if an identifier is a local variable (function arguments are local variables) if not it checks if it is a member of the environment object (this).

For instance:

function testy(arg)
{
    local a=10;
    print(a);
    return arg;
}			
			

will access to local variable 'a' and prints 10.

function testy(arg)
{
    local a=10;
    return arg+foo;
}
			

in this case 'foo' will be equivalent to 'this.foo' or this["foo"].

Global variables are stored in a table called the root table. Usually in the global scope the environment object is the root table, but to explicitly access the global table from another scope, the slot name must be prefixed with '::' (::foo).

exp:= '::' id

For instance:

function testy(arg)
{
    local a=10;
    return arg+::foo;
}
			

accesses the global variable 'foo'.

However (since squirrel 2.0) if a variable is not local and is not found in the 'this' object Squirrel will search it in the root table.

function test() {
	foo = 10;
}

is equivalent to write

function test() {
	if("foo" in this) {
		this.foo = 10;
	}else {
		::foo = 10;
	}
}