Something which is definitely a feature, being a logical consequence of
the language and documented, is that a missing value for a logical
expression is treated as "true". However, I tripped over on it and that
made me wonder if it is a dangerous feature - the implication is that any
program must guard against the possibility. Consider, for example the
consequences of missing data in code such as:
if wmd invade x
where x is a string variable.
One approach is a self-imposed discipline to make a rigorous logical
variable and test:
if wmd==1 ...
R. Allan Reese Email: [email protected]
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