LB Booster: I wrote a wrong code!

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I wrote a wrong code!
Post by SarmedNafi on Aug 9^th, 2015, 03:54am

The following code which I wrote is wrong.

But it is accepted by LBB and run it in wrong way, so a wrong result was displayed.

Code:


'code------
A=4

if A=2 then else print "3"
  print "2"
else
if A=4 then 
  print "4"
end if
end if

wait
'code-----

I hope Richard will take care of it at next release.

With all thanks to Richard
Regards,
Sarmed

Re: I wrote a wrong code!
Post by Richard Russell on Aug 9^th, 2015, 07:11am

on Aug 9^th, 2015, 03:54am, SarmedNafi wrote:

I hope Richard will take care of it at next release.

It's unlikely, I'm afraid - BBC BASIC also accepts the equivalent program without reporting any error!

Richard.

Re: I wrote a wrong code!
Post by sirguylittle on Aug 10^th, 2015, 7:05pm

First things first, Hi all. I have been lurking on this forum for long enough, so thought I would introduce myself and chip in :)

on Aug 9^th, 2015, 03:54am, SarmedNafi wrote:

I hope Richard will take care of it at next release.

It would be quite difficult I think for a compiler to catch errors like this where the error stretches over multiple statements and is more due to faulty logic rather than a syntax error.

I believe this is why it is suggested that when constructs such as IF... THEN... ELSE... are used, that you do not mix the use of single line statements with multiple line ones.
IE either use IF... THEN... ELSE... on one line or use
IF... THEN
...
ELSE
...
END IF

but do not mix them.
For one thing, it will make your program easier to read and debug later and I think the separate line form is to be preferred for this reason.

In your particular example, SELECT CASE might be a better choice instead of using nested IF... THEN... ELSE... constructs.

Code:

A=4

SELECT CASE A
    CASE 2
        PRINT "2"
    CASE 3
        PRINT "3"
    CASE 4
        PRINT "4"
    CASE else
        PRINT "something else"
    END SELECT