A word requiring an input didn't get one from the word
following it in an instruction line. In the following
example, forward needs an input.
forward pd
MicroWorlds looks to the right to find a number. It runs
pd hoping that this is a word that will report
a number. Pd doesn't report a number and
MicroWorlds complains:
pd didn't report anything to forward
Here's an example that works:
forward slider1
In this case, slider1 reports a number that
forward is able to use.