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
When SBASIC was first mooted, I remember that there was at the time
discussion that other BASICs gave variables default zero value rather than
stopping with an error - "why couldn't the QL do this?"
Don't know if that influenced Tony Tebby to make SBASIC variables behave in
this way or not, or was that just coincidence?
Dilwyn
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