Strange problem caused by extra space characters

[Harvey Shulman]

I wonder if this is a well known problem to everyone but me ?  We
created a list structure that included our stimulus words and an
attribute named corr_resp that contained the required keypress for each
stimulus.   The two values used for corr_resp are {UPARROW} and {DOWNARROW}.

We then specified in the textdisplay that presented the stimulus that
the allowable responses were {UPARROW}{DOWNARROW} and the
correctresponse was [corr_resp].

This worked just fine until we added some new stimuli and then the
program would hit a run-time error with the message that the
correctresponse was not in the allowable set.   This could be fixed by
changing the allowable set to {ANY} but why was it happening ?

The answer turned out to be that in adding new stimuli to our list we
had sometimes entered the value of corr_resp as {UPARROW}__  where __
was just one or two (invisible) space characters after the bracket.
Erasing them fixed the problem.

I find this a very strange 'feature' in EPRIME.  The trailing spaces are
being interpreted as part of the code for a correct response.  Is there
a benefit to this feature or is it just an oversight in parsing the
correct response field in the text display ?

--
Dr. Harvey G. Shulman
Department of Psychology
Ohio State University
Columbus, OH 43210
fax 614 688-3984  ph 614 292-2759