[PYTHON MATRIX-SIG] A problem with slicing
Jim Fulton, U.S. Geological Survey
jfulton@usgs.gov
Thu, 14 Sep 1995 10:50:25 -0400
On Thu, 14 Sep 1995 10:39:00 -0400
Guido van Rossum said:
> > I really don't see any reason why the matrix type should require
> > language changes (aside from the minor impact of the tuplefication
> > operator).
>
> I guess one of my points was that, given the desire for a fairly
> consistent design, allowing tuples as indices is *not* a minor
> change...
I'm not suggesting that tuples should be allowed as indexes to
sequence types. Tuples are *already* allowed as indexes to mapping
types. I propose that matrices should provide *both* sequence and
mapping behavior, where the mapping behavior is used to support matrix
slicing. This requires *no* change to the language.
The only *minor* change proposed, which I could live without is to
allow the "," to generate tuples inside of []s, just as it does
outside of []. In fact, I view the current non-recognition of tuples
in []s as an inconsistency. For example:
a=1,2,3
is equivalent to:
a=(1,2,3)
and:
for spam in 1,2,3:
...
is equivalent to:
for spam in (1,2,3):
...
so why isn't:
a[1,2,3]
equivalent to:
a[(1,2,3)
Note that this change is cosmetic (like making modules callable ;-),
and is not *needed* for the matrix proposal.
Jim
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