Operator Address of

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Operator @ (Address Of)

Returns the address of a string literal, variable, object or procedure

Syntax

Declare Operator @ ( ByRef rhs As T ) As T Pointer

Parameters

• rhs
• T

Description

Operator @ (Address of) returns the memory address of its operand.

When the operand is of type String, the address of the internal string descriptor is returned. Use Operator Strptr (String pointer) to retrieve the address of the string data.

The operand cannot be an array, but may be an array element. For example, "@myarray(0)" returns the address of "myarray(0)".

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

Return Value

Returns the address of the right-hand side (rhs) operand.

Remarks

Usage

result = @ rhs

Dialect Differences

• In the -lang qb dialect, this operator cannot be overloaded.

Differences from QB

• New to FreeBASIC

See also

• VarPtr
• ProcPtr
• Operator * (Value Of)

Examples

'This program demonstrates the use of the @ operator.

Dim a As Integer

Dim b As Integer

Dim addr As Integer Ptr

a = 5   'Here we place the values 5 and 10 into a and b, respectively.

b = 10

'Here, we print the value of the variables, then where in memory they are stored.

Print "The value in A is ";a;" but the pointer to a is ";@a

Print "The value in B is ";b;" but the pointer to b is ";@b

'Now, we will take the integer ptr above, and use @ to place a value into it.

'Note that the * will check the value in the ptr, just as @ checked the ptr

'for a normal variable.

addr = @a

Print "The pointer addr is now pointing at the memory address to a, value: ";*addr

addr = @b

Print "The pointer addr is now pointing at the memory address to b, value: ";*addr

'This program demonstrates how the @ symbol can be used

'to create pointers to subroutines.

Declare Sub mySubroutine ()

Dim say_Hello As Sub()

say_Hello = @mySubroutine   'We tell say_Hello to point to mySubroutine.

                            'The sub() datatype acts as a pointer here.

say_Hello() 'Now we can run say_Hello just like mySubroutine.

Sub mySubroutine

    Print "hi"

End Sub

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Category: Operators
Kind: operator

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Reproduced from the FreeBASIC Wiki Manual under the GNU Free Documentation License 1.3 — with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. Copyright © the FreeBASIC project and wiki contributors. See License.