Mikroelektronika MIKROE-724 データシート

mikroBasic PRO for dsPIC30/33 and PIC24

MikroElektronika

209

Example  demonstrates  the  usage  of  function  pointers.  It  is  shown  how  to  declare  a  procedural  type,  a  pointer  to 

function and finally 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, define the procedural type

dim MyPtr as ^TMyFunctionType  ‘ This is a pointer to previously defined type

dim sample as word

sub function Func1(dim p1, p2 as byte, dim p3 as word) as word ‘ Now, define few functions 

which will be pointed to. Make sure that parameters match the type definition

  result = p1 and p2 or p3

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 definition

  result =  abc * def + ghi

sub function Func3(dim first, yellow as byte, dim monday as word) as word  ‘ Yet another 

function. Make sure that parameters match the type definition

  result =  monday - yellow - first

‘ 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

@ 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 first 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 first basic element.