Pointers

FUNCTION and SUB Pointers

Example 1:


 
 GLOBAL Func(DUMMY AS INTEGER) AS FUNCTION INTEGER
 
 SetFunc(x0)
 ? Func(2)
 
 SetFunc(x1)
 ? Func(2)
 
 
 SUB SetFunc (f AS Func_TYPE)
   Func = f
 END SUB
 
 '-----------------------------------------------

 FUNCTION x0(x AS INTEGER) AS INTEGER
   FUNCTION = x * x
 END FUNCTION
 
 
 FUNCTION x1(x AS INTEGER) AS INTEGER
   FUNCTION = x * x * 2
 END FUNCTION

Result:


 4
 8

Example 2:


  GLOBAL PTR_Funcs () AS FUNCTION INTEGER
  
  SET Funcs[] AS PTR_Funcs_TYPE   ' BCX creates a typedef and tacks on "_TYPE" to the declaration  
   x0,
   x1,
   x2,
   x3,
   x4
  END SET
   
  FUNCTION x0
    FUNCTION = 0
  END FUNCTION
  
  FUNCTION x1
    FUNCTION = 1
  END FUNCTION
  
  FUNCTION x2
    FUNCTION = 2
  END FUNCTION
  
  FUNCTION x3
    FUNCTION = 3
  END FUNCTION
  
  FUNCTION x4
    FUNCTION = 4
  END FUNCTION
  
  '------------------------ 
 
  DIM i
  
  FOR i = 0 TO 4
    ? Funcs[i]()
  NEXT

Result:

Example 3:


  GLOBAL PTR_Funcs () AS FUNCTION PCHAR
   
  SET Funcs2[] AS PTR_Funcs_TYPE   ' BCX creates a typedef and tacks on "_TYPE" to the declaration  
   s0$,
   s1$,
   s2$,
   s3$,
   s4$
  END SET
  
  FUNCTION s0$
    FUNCTION = "0"
  END FUNCTION
  
  FUNCTION s1$
    FUNCTION = "1"
  END FUNCTION
  
  FUNCTION s2$
    FUNCTION = "2"
  END FUNCTION
  
  FUNCTION s3$
    FUNCTION = "3"
  END FUNCTION
  
  FUNCTION s4$
    FUNCTION = "4"
  END FUNCTION
  
  '----------------------- 
 
  DIM i
  
  FOR i = 0 TO 4
    ? Funcs2$[i]()
  NEXT

Result:

Example 4:


  GLOBAL PF_1_ARG(DUMMY AS INTEGER) AS FUNCTION INTEGER
  
  SET Funcs3[] AS PF_1_ARG_TYPE
    n0,
    n1,
    n2,
    n3,
    n4
  END SET
  
  FUNCTION n0(n AS INTEGER)
    FUNCTION = n * 0
  END FUNCTION
  
  FUNCTION n1(n AS INTEGER)
    FUNCTION = n * 1
  END FUNCTION
  
  FUNCTION n2(n AS INTEGER)
    FUNCTION = n * 2
  END FUNCTION
  
  FUNCTION n3(n AS INTEGER)
    FUNCTION = n * 3
  END FUNCTION
  
  FUNCTION n4(n AS INTEGER)
    FUNCTION = n * 4
  END FUNCTION
  
  '------------------------------ 
 
  DIM i
  
  FOR i = 0 TO 4
    ? Funcs3[i](i)
  NEXT

Result:

Example 5:


 DIM y(s$,j$) AS SUB
 
 y = xx : CALL xx ( "hello"  , " world" ) '  It is OKAY to use the CALL  keyword

 y = zz : zz ( "goodbye" , " cruel world" ) '  Using the CALL keyword is not required

 SUB xx (a$, j$)
   PRINT
   PRINT UCASE$(a$),UCASE$(j$), ":-)"
 END SUB
 
 SUB zz (a$, j$)
   PRINT
   PRINT MCASE$(a$),MCASE$(j$)," :-("
 END SUB

Result:


 HELLO WORLD:-)

 Goodbye Cruel World :-(