https://github.com/jrincayc/ucblogo-code
Tip revision: e494a4e0c0e335b25b7436b36075800bcc1657c0 authored by Dan Malec on 05 September 2024, 01:42:59 UTC
Merge pull request #185 from jrincayc/artifacts
Merge pull request #185 from jrincayc/artifacts
Tip revision: e494a4e
dmaybeoutput
.MAYBEOUTPUT value (special form)
works like OUTPUT except that the expression that provides the
input value might not, in fact, output a value, in which case
the effect is like STOP. This is intended for use in control
structure definitions, for cases in which you don't know whether
or not some expression produces a value. Example:
to invoke :function [:inputs] 2
.maybeoutput apply :function :inputs
end
? (invoke "print "a "b "c)
a b c
? print (invoke "word "a "b "c)
abc
This is an alternative to RUNRESULT. It's fast and easy to use,
at the cost of being an exception to Logo's evaluation rules.
(Ordinarily, it should be an error if the expression that's
supposed to provide an input to something doesn't have a value.)