Operator [] (Pointer Index)

Returns a reference to memory offset from an address

Syntax
	KeyPgDeclareDeclare KeyPgOperatorOperator [] ( KeyPgByrefByRef lhs KeyPgAsAs T KeyPgPtrPointer, KeyPgByrefByRef rhs KeyPgAsAs KeyPgIntegerInteger ) 
	KeyPgByrefFunctionByRef KeyPgAsAs T

Usage
		result = lhs [ rhs ]
	or
		lhs [ rhs ] = value

Parameters
	lhs
		The base address.
	rhs
		A signed offset from lhs.
	T
		Any data type.

Description
	This operator returns a reference to a value some distance in memory 
	from a base address. It is essentially shorthand for "KeyPgOpValueOf*(lhs KeyPgOpAdd+ rhs)" 
	because the reference can be thought of as a pointer having as value the 
	memory location "(lhs KeyPgOpAdd+ rhs)", and which is implicitly dereferenced; 
	both do exactly the same thing.
	Like pointer arithmetic, any type of KeyPgPtrPointer can be indexed except for 
	an KeyPgAnyAny KeyPgPtrPointer. Also, like pointer arithmetic, it is up to the user to 
	make sure meaningful data is being accessed.

	When indexing a '2-dimensional' pointer (i.e. a T Ptr Ptr), the first 
	(leftmost) index is applied before the second: For example, Pt[I1][I2] = 
	*(Pt[I1] + I2) = *(*(Pt + I1) + I2)
	In general, when using an 'n-dimensional' pointer: Pt[I1][I2].....[In], 
	the index order (from left to right) corresponds to the dereferencing 
	order.

	This operator must not be used in case of null pointer because reference 
	is undefined (inducing runtime error).
	Otherwise, the user must ensure that the offset value (rhs) is in a 
	range that allows an access to valid memory. Outside this range, results 
	are undefined.

	This operator can be overloaded for user-defined types as a member 
	KeyPgOperatorOperator using the appropriate syntax.

Example
	'' initialize a 5-element array
	Dim array(4) As Integer = { 0, 1, 2, 3, 4 }

	'' point to the first element
	Dim p As Integer Ptr = @array(0)

	'' use pointer indexing to output array elements
	For index As Integer = 0 To 4
	   Print p[index];
	Next
	Print

	Will give the output,

	 0 1 2 3 4

Differences from QB
	* New to FreeBASIC

See also
	* ProPgPtrArithmeticPointer Arithmetic
	* KeyPgOpValueOfOperator * (Value Of)
	* KeyPgOpStringIndexOperator [] (String Index)
	* KeyPgOpArrayIndexOperator () (Array Index)
	* KeyPgOpAddOperator + (Add)
	* KeyPgOpSubtractOperator - (Subtract)
	* CatPgOpPointPointer Operators

