Kaleidoscope in BASIC

But only with BASIC$Crunch set for BASIC V

I thought that was the default, but now that I check, it seems not to be set.

The advocates for not crunching distributed code usually state that it isn’t necessary because it happens as standard on recent versions of the OS…?

each DEFPROC must have one and only one ENDPROC marking the end of the procedure code.

Except that in my User Guide of 1991 and the current PDF manual it says:

“An ENDPROC which is nested within some other structure will be compiled as a branch to the ‘real’ end of the procedure.”

And interestingly, it is possible to compile a DEF PROC with no ENDPROC with directive {NOTRAPS}. ;-)

Gosh, it is so very long ago I explored all the quirks of ABC, before giving it up as a lost cause once I had some assembly under my belt.

each DEFPROC must have one and only one ENDPROC marking the end of the procedure code.

Wow, that’s delightfully ambiguous. Yes, only one ENDPROC ends a procedure, but there might be several of them in the procedure with the first one encountered in the code path being the end of the procedure.

LOCAL variables are only in scope in the body of the procedure

Yeah, we know. ;-)

No LOCAL error handling is permitted, all error handling throws away any LOCAL variables and stack usage and does not know the original line number.

So I suppose this means code has to be rewritten to use X-form SWIs and check return codes. In other words, nobbling some of BASIC’s nice localised error handling and turning it into C (do something, did it fail? do something else, did it fail?).

Correct. The manual explains that ABC cannot do this.

ABC just built this:

PROCmeh(1)
END

DEFPROCmeh(what%)
  IF (what% < 1) THEN ENDPROC
  IF (what% > 1) THEN ENDPROC
  PRINT "It's one!"
ENDPROC

The advocates for not crunching distributed code usually state that it isn’t necessary because it happens as standard on recent versions of the OS…?

I think it’s supposed to be done by BASIC VI (but not BASIC V), however a quick look in the FP and VFP module shows the string Basic$Crunch, so maybe they all behave the same?
Or maybe it only happens automatically in certain situations where it’s clear that access to the source form isn’t wanted (or necessarily easy to access), such as LIBRARY and BASIC -quit ?

it is so very long ago I explored all the quirks of ABC

:-)

ABC just built this

Of course, because:

“An ENDPROC which is nested within some other structure will be compiled as a branch to the ‘real’ end of the procedure.”

;-)

Or maybe it only happens automatically in certain situations where it’s clear that access to the source form isn’t wanted (or necessarily easy to access), such as LIBRARY and BASIC -quit ?

Automatic crunching only ever happens in those two circumstances (see the manual) for the very rationale you suggest.

However, it still requires the system variable to be set for BASIC V, but not for VI.

FP and VFP module shows the string Basic$Crunch

I imagine the string remains in all modules simply because it is easier not to specially omit it when not required.