There is such a thing as overdoing GOTOs, but I agree that a blanket
never-do-it rule is counter-productive. I don't often use SIGNAL in REXX,
because I find that its structured features are adequate. But in other
languages I have argued for limited GOTO use.
In COBOL, for example, it seems to me that there's a place for GOTO
TOP-OF-PARAGRAPH (to simulate ITERATE in REXX), GOTO EXIT-PARAGRAPH (to
simulate LEAVE) and GOTO END-OF-PROGRAM (for controlled abend conditions).
These don't violate structured-programming principles, they implement them. In
VBA I freely use Goto IterateSomething (putting the label just before the Next
statement). I don't think PL/1 ever needs it, but I'm glad it's there just in
case.
Even in REXX there's one missing structured ingredient: some way to leave a
~simple~ block. A SELECT comes close, but it's not perfect. Say you're
looping through a list of candidates and have to perform a number of candidates:
do jr=1 to stem.0
v0=stem.jr
if v0='' then iterate
v1=function1(v0)
if v1<5 then iterate
v2=functionv2(v1 + othervalue)
if v2=previous then iterate
say 'TRK:' v0 v1 v2
end
That's great in a controled DO loop. But it's harder in simple block of code.
A SELECT won't do the job, because of the calculations you have to do between
the various tests. I handle it this way:
do 1
if v0='' then leave
v1=function1(v0)
if v1<5 then leave
v2=functionv2(v1+othervalue)
if v2=previous then leave
say 'TRK:' v0 v1 v2
end
I always suspect I'd get complaints from structured enthusiasts if they ever
saw me cheating like that. In VBA I can't "Do 1", but I can do this:
Do 'one time
If v0 = '' Then Exit Do
v1 = function1(v0)
If v1 < 5 Then Exit Do
v2 = functionv2(v1 + othervalue)
If v2 = previous Then Exit Do
MsgBox "TRK: " & v0 & " " & v1 & " " & v2
Loop Until True
---
Bob Bridges, [email protected], cell 336 382-7313
/* Being famous has its benefits, but fame isn't one of them. -Larry Wall */
-----Original Message-----
From: David Crayford
Sent: Tuesday, March 24, 2020 09:03
If you eschew goto how do you deal with error handling and cleanup using
a language which doesn't support exceptions, finalization or RAII? I find
these kind of blanket rules to lead to bad code with deep nesting and useless
status variables.
--- On 2020-03-21 11:45 PM, Paul Gilmartin wrote:
> o Symbols EXPOSEd from external scopes can't be used as targets
> of ITERATE and LEAVE. (I eschew GOTO; SIGNAL is worse,)
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