Hi Lars,
Sorry for the disturbance I cause but I still can not get the pairglob
function right it seems. The definition I sent you a few days ago used
a case construction which is unneccesary in the presence of the selectors
(eliminators) globroot and globchild. So I wrote a new pairglob using
globroot and globchild instead in hope for more success, but nope I can
not get it right.
Is there somewhere I can read more about the rec operator (gadget)?
I am sure this deserves a longer answer, but here is a short but quick
one: rec implements structural recursion
and this can only be recognized if the argument has been analyzed using
case. Hence you should not replace
case by selectors. There are other reasons why selectors are less useful
in Epigram than in conventional functional
programming: using case you test and select at the same time, using
selectors this connection is given up and you
need explicit reasoning to establish that your program is well-behaved.
E.g. if you read Conor's tutorial
http://www.e-pig.org/downloads/epigram-notes.pdf
this is basically the opening gambit. This also contains a detailed
explanation how rec works, e.g. have
a look at the material around p.13.
It would be interesting to find out what you are up to. I am afraid I
don't actually know what globular sets
are and what they are good for.
Cheers,
Thorsten
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