Ken Dickey wrote:
On Sunday 19 October 2008 15:16:47 Thomas Lord wrote:
Why do you need the extra baggage of "sequences of length greater than or
equal to two?"
The difference is in the term "sequence" which is not mentioned in (e.g.) R6RS
numeric discussions.
I have done plenty of sorting, but have never used Scheme seriously for
numeric sequences. My usages are more typically something like:
(if (< lo-bound x high-bound) ... )
This seems hypocritical to me.
On the one hand, you don't want to allow 0 or 1 argument because
you see < as a binary relation and those cases don't make sense
unless we're treating < as sequence predicate. You want the error
checking to rule out 0 or 1 arguments to avoid "surprise" to
someone who sees a binary operator there.
On the other hand, you'll allow 3 arguments because it is
convenient and in spite of the fact that it rules out error checking
for someone who sees a binary operator there.
I don't consider (low-bound x high-bound) to be a sequence
Parameter lists satisfy any reasonable axiom system for finite
sequences so they are such regardless of whether or not you give
the matter your consideration.
But, now you have a "consideration deficit". I can easily "explain"
the meaning of (< a b c) by referring to a binary relation and its
natural extension to finite sequences -- but then I'll also explain
(<) and (< a) so you'll still owe explanation of why just those two
cases get ruled out. On the other hand, if the natural extension to
finite sequences is not *your* explanation for (< a b c ...) you
owe *that* explanation.
Your selection of what to call an error seems to me on a shaky
ground of trying to predict "common cases" rather than asking
how to make clean models.
(unless a sequence
of lexical tokens--but that again is a different domain).
Parameter lists and the results of unpacking lists into parameters
used by "apply" are, at run time, semantically finite tuples, or
finite lists, or finite sequences -- all the same thing.
-t
Yes. This is a difference in perspective -- and usage.
-KenD
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