|Rapid-Q Documentation by William Yu (c)1999
||Appendix C: Trouble Shooting
How to debug your programs
In most cases, it's either a typo, or you're trying to use a function
which is not supported under Rapid-Q. This occurs most often when you don't have
$TYPECHECK ON. I can't stress this enough, unless you've used Rapid-Q for awhile,
I strongly encourage everybody to turn this directive on. Rapid-Q has a very poor
checking mechanism, and relies heavily on the programmer to write proper code.
SPC is not supported in Rapid-Q (in QBasic, SPC just skips spaces). If typechecking
is off, the above statement is perfectly valid. SPC is a variable, initialized
to 0, and (10) has no effect (ie. the number 10 is pushed on the stack, but no operation
is done), so the above output will be 0.
Passing by reference
Only QObjects, Arrays, and Variants are passed by reference, all other variables are
passed by value. To pass a variable by reference, you can either explicitly
specify this by adding BYREF to your parameter list, or prepend an @ symbol
to any variables you want passed by reference when calling the function.
Do not use the @ symbol for Arrays, Variants, or QObjects since they are passed by reference
by default. Read more about this in Chapter 3 or Appendix C: Procedures.
Typechecking is done only for Arrays, Variants, and QObjects, since
you can't pass an array of integers to a SUB that expects an array of doubles.
You should get an error message if you try this, however, for all other variables
which are passed by value, NO checking is done. Which means you could easily
pass an integer to a SUB expecting a string. So becareful that you know the type of
parameters for your SUB/FUNCTION, since Rapid-Q won't complain. Also make sure if
you have DECLARE SUBs, that your SUB will have matching parameters, including
matching parameter names.
Using Undocumented features
Rapid-Q has some undocumented features, most of which are in a beta-like stage.
You can embed SUBs or FUNCTIONs but they can only be one level deep, and there
are some consequences with using them. If you don't know what an embedded SUB
looks like, take this for example:
DIM I AS INTEGER
SUB MyChildSub (X AS INTEGER)
DIM N AS DOUBLE
PRINT "In Child Sub"
There are some special issues involved, such as all variables are local to the
SUBs that follow. Meaning, the variable I is local to SUB MyChildSub.
Also, since Rapid-Q doesn't actually clean things up, you can actually
call MyChildSub in your main program as well. This is a problem I'm
working to correct when I find the time. One other feature which might interest
people is postfix ++ and --
DIM I AS INTEGER
I++ '-- same as I = I + 1
I-- '-- same as I = I - 1
I -= 10 '-- same as DEC(I, 10)
I += 15 '-- same as INC(I, 15)
Arrays are a special case, anything but Arrays can be incremented/decremented.
Rapid-Q doesn't do any optimizing, so the above code and the given translation
runs exactly the same.
If you don't have a clue as to what is causing your programs to crash, your
only hope is to put several PRINT statements in your program and incrementally
check each block of code so that it works properly. If you're using Unix or Linux,
try using gdb, sometimes it will give you some useful information, but most
of the time it's not really that helpful in this kind of setting.