On Feb 21, 2012, at 5:41 AM, Stephen Bloch wrote: > On Feb 21, 2012, at 7:18 AM, Rodolfo Carvalho wrote: > >> BTW I just found the nested-cond pattern appearing on HtDP, throughout >> section 9: >> http://htdp.org/2003-09-26/Book/curriculum-Z-H-13.html > > That happens when you follow the HtDP design recipe directly and there are > conditionals for two unrelated reasons, e.g. > > (cond [(empty? L) ...] > [(cons? L) > (cond [(snark? (first L)) ...] > [(boojum? (first L)) ...] > [(beeblebrox? (first L)) ...] > )]) > > Yes, this COULD be collapsed into > (cond [(empty? L) ...] > [(snark? (first L)) ...] > [(boojum? (first L)) ...] > [(beeblebrox? (first L)) ...] > ) > but that doesn't match the data structure as transparently.
+1. I tell my students to ollapse the cond *only* when it makes more sense in the collapsed form---it rarely does. John Clements
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