User manual

mikroBasic PRO for dsPIC30/33 and PIC24
MikroElektronika
209
Example:
Example demonstrates the usage of function pointers. It is shown how to declare a procedural type, a pointer to
function and nally how to call a function via pointer.
program Example;
typedef TMyFunctionType = sub function (dim param1, param2 as byte, dim param3 as word)
as word ‘ First, dene the procedural type
dim MyPtr as ^TMyFunctionType ‘ This is a pointer to previously dened type
dim sample as word
sub function Func1(dim p1, p2 as byte, dim p3 as word) as word ‘ Now, dene few functions
which will be pointed to. Make sure that parameters match the type denition
result = p1 and p2 or p3
end sub
sub function Func2(dim abc, def as byte, dim ghi as word) as word ‘ Another function of
the same kind. Make sure that parameters match the type denition
result = abc * def + ghi
end sub
sub function Func3(dim rst, yellow as byte, dim monday as word) as word ‘ Yet another
function. Make sure that parameters match the type denition
result = monday - yellow - rst
end sub
‘ main program:
main:
MyPtr = @Func1 ‘ MyPtr now points to Func1
Sample = MyPtr^(1, 2, 3) ‘ Perform function call via pointer, call Func1, the return
value is 3
MyPtr = @Func2 ‘ MyPtr now points to Func2
Sample = MyPtr^(1, 2, 3) ‘ Perform function call via pointer, call Func2, the return
value is 5
MyPtr = @Func3 ‘ MyPtr now points to Func3
Sample = MyPtr^(1, 2, 3) ‘ Perform function call via pointer, call Func3, the return
value is 0
end.
@ Operator
The @ operator constructs a pointer to its operand. The following rules are applied to @:
- If X is a variable, @X returns a pointer to X.
Note: If variable X is of array type, the @ operator will return pointer to it’s rst basic element, except when the left side
of the statement in which X is used is an array pointer.
In this case, the @ operator will return pointer to array, not to it’s rst basic element.