Hi all,

When QDOS evaluates an expression and encounters a variable with no value 
assigned, it STOPs with “error
in expression” and reports the line number.  The programmer may well have made 
some spelling mistake, and can immediately make a correction.  QDOS is doing 
exactly what the programmer wants.

Can SMSQ/E be upgraded to follow suit?  

Currently, in the above-mentioned case, SMSQ/E will use a zero value and will 
carry on blindly with no error reported.  The assumption is made that any new 
variable will have a default value of zero.  This behaviour does not take 
account of the fact that people are human and will sometimes make spelling 
mistakes.  The unintentional mistake gets buried and lost in the middle of the 
code.  I can spend a great deal of time and effort composing a program; I can 
type it all in, and can even double check it, but I can still overlook things.  
After writing a program in SMSQ/E, I can never be certain that it is free of 
typos.  There is this constant anxiety in the mind.  Programming can be 
difficult, even without the additional workload required of having to track 
down possible spelling mistakes, when there might be none at all - one can 
never tell.  QDOS is much friendlier in this respect.  This is why I would like 
for SMSQ/E to be upgraded to act like QDOS.  If this would entail a slight loss 
of efficiency, then that would be acceptable.  For me, the most important 
aspect of programming is to be able to write code that is going to work as 
intended.  If SMSQ/E could be upgraded, then this would mean that all new 
variables would need to be initialised with values before
they are used.  This would apply to both global and local variables in 
procedure/functions.  However, this is a recognised good practice in any case.  
It is good practice because these initialisations are being documented.  We 
have to remember that others will want to look at and understand the code we 
write.  SMSQ/E would be enforcing this desirable state of affairs, as QDOS does.

Michael Bulford
QL-Users Mailing List

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