Macros and Error Checking

[Knuth Konrad]

Let me add three words that may help clarifying what's going on when ...

The difference between a MACRO and a SUB or FUNCTION is that a macro is not a discreet code module. It is simply text substition at compile time in your code.

[Bud Durland]

The difference between a MACRO and a SUB or FUNCTION is that a macro is not a discreet code module. It is simply text substition in your code. Consider this:

' Constants can't be floating point, so we do this 
MACRO Pi = 3.1415926

' Sometimes, PB's banker's rounding is not appropriate
MACRO RoundUp(TheNumber) = Round(TheNumber+0.0001,3)

FUNCTION PBMAIN() as LONG

  STDOUT Pi

  STDOUT RoundUp(5.46)

END FUNCTION

The above PBMAIN routine will be compiled as if you entered it like so:

FUNCTION PBMAIN() as LONG

  STDOUT 3.1415926

  STDOUT Round(5.46+0.0001,3)

END FUNCTION

Hope this helps

[Kev Peel]

Cliff,

Using a MACRO in code will simply replace the name of the MACRO with it's contents. A few examples:

 
MACRO BIGINTEGER = QUAD
 
[..]
 
' "BIGINTEGER" will be replaced with the contents of the "BIGINTEGER" macro...
DIM BIG AS BIGINTEGER 
 
 
MACRO RETURN(X)
  FUNCTION = X
  EXIT FUNCTION
END MACRO
 
[..]
 
' "RETURN" will be replaced with the contents of the "RETURN" macro...
FUNCTION PBMAIN
  RETURN(-1)
END FUNCTION
 
 
 
MACRO PATHONLY(s) = LEFT$(S, INSTR(-1, S, ANY "\/")-1)
 
[..]
 
' "PATHONLY" will be replaced with the contents of the "PATHONLY" macro...
s = "C:\AUTOEXEC.BAT"
? PATHONLY(s)

[Cliff Nichols]

Kev,
If I read you right then Macro in this case I may as well build a Sub? or a Function? (Guessing Sub since I do not think Macro's return anything? unless a variable is set to = some value that is)

Maybe I still dont get it, but starting to think a macro is nothing more than a sub with a different name?

[Kev Peel]

A PowerBASIC MACRO is not like an Excel "macro" where you have predefined code snippet that performs an action, it is simply text substitution.

Example:

Macro ShowText(s)
  #if %def(%PB_CC32)
      PRINT S
      WAITKEY$
  #else
      MSGBOX S
  #endif
End Macro
 
Function Pbmain
  ShowText("show this text")
  ShowText("show that text")
End Function

[Cliff Nichols]

I will admit when it comes to Macro's I just don't get it. My only experience with them was in Excel over 10 yrs ago and that was just "Recording" the steps I took to do some calculation.

If I understand correctly, a macro can be used to "Insert" code into my functions at compile time? If this is the case I have an idea that may or may not work.

If I have functions like the pseudo-code below

Function DoSomething1() AS LONG
     'Do Something here and return a long
End Function

Function DoSomething2() AS STRING
     'Do Something here and return a String
End Function

Can I add a macro to do something like

macro
     Insert "On Error Goto ErrorHandler" as the 1st line in each function
     Insert "Exit Function" or "Exit Sub" on the line above my label for "ErrorHandler"
     Insert the label "Error Handler"
     Insert whatever error handling routines I need
end macro

Function DoSomething1() AS LONG
     'Do Something here and return a long
End Function

Function DoSomething2() AS STRING
     'Do Something here and return a String
End Function

so that in essence it would be like I added the code to each Function/Sub myself that the layout would look something like

Function DoSomething1() AS LONG
     ON ERROR GOTO ErrorHandler
     'Do Something here and return a long
     EXIT FUNCTION
ErrorHandler:
     'Error Handling routines
End Function

Function DoSomething2() AS STRING
     ON ERROR GOTO ErrorHandler
     'Do Something here and return a String
     EXIT FUNCTION
ErrorHandler:
     'Error Handling routines
End Function

This may be an easy answer, or maybe I am way off base, but had to ask