Wiki source for KeyPgOpValueOf


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{{fbdoc item="title" value="Operator * (Value of)"}}----
Dereferences a pointer

{{fbdoc item="syntax"}}##
[[KeyPgDeclare|declare]] [[KeyPgOperator|operator]] ***** ( [[KeyPgByref|byref]] //rhs// [[KeyPgAs|as]] //T// [[KeyPgPtr|pointer]] ) [[KeyPgByrefFunction|byref]] [[KeyPgAs|as]] //T//
##

{{fbdoc item="usage"}}##
//result// = * //rhs//
##
{{fbdoc item="param"}}
##//rhs//##
The address to dereference.
##//T//##
Any [[CatPgStdDataTypes|standard]], [[CatPgUserDefTypes|user-defined]] or procedure type.

{{fbdoc item="ret"}}
Returns a reference to the value stored at the address ##//rhs//##.

{{fbdoc item="desc"}}
**##Operator *## (Value of)** returns a reference to the value stored at an address, and is often called the dereference operator. The operand is not modified in any way.
Any type of ##[[KeyPgPtr|Pointer]]## can be dereferenced except for an ##[[KeyPgAny|Any]]## ##[[KeyPgPtr|Pointer]]##.

As a reference, the result of this operator can be used on the left-hand side of assignments.

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 pointer value induces access to a valid memory. Otherwise, results are undefined.

This operator can be overloaded for user-defined types.

{{fbdoc item="ex"}}
{{fbdoc item="filename" value="examples/manual/operator/valueof.bas"}}%%(freebasic)
'This program demonstrates the use of * to utilize the value a pointer points to.
Dim a As Integer
Dim pa As Integer Ptr

pa=@a 'Here, we use the @ operator to point our integer ptr at 'a'.
' 'a' is, in this case, a standard integer variable.

a=9 'Here we give 'a' a value of 9.

Print "The value of 'a' is";*pa 'Here, we display the value of 'a' using a pointer.

*pa = 1 'Here we use our pointer to change the value of 'a'
Print "The new value of 'a' is";a 'Here we display the new value of 'a'.
%%
Output:
%%
The value of 'a' is 9
The new value of 'a' is 1
%%

{{fbdoc item="lang"}}
- In the //[[CompilerOptlang|-lang qb]]// dialect, this operator cannot be overloaded.

{{fbdoc item="diff"}}
- New to ""FreeBASIC""

{{fbdoc item="see"}}
- ##[[KeyPgOpAt|Operator @ (Address of)]]##
- ##{{fbdoc item="keyword" value="KeyPgOpPtrIndex|Operator [] (Pointer index)"}}##
- [[ProPgPointers|Pointers]]

{{fbdoc item="back" value="CatPgOpPoint|Pointer Operators"}}{{fbdoc item="back" value="CatPgOperators|Operators"}}
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