[PYTHON MATRIX-SIG] Slices

[Konrad HINSEN]

> There are problems with this as I found when initially considering
> such a possibility.  If ":" notation is allowed wherever a "test"
> expression can occur then there can be ambiguity with statements where
> ":" is used to introduce a compound statement, i.e. in "for" or "if"
> statements. 

I see. That's of course a good argument.

> I think that we will have to go with option (2).  However, the
> interface to Slice() should change to duplicate ":" rather than have
> the old interface.

But that is rather difficult with standard function-call syntax.

Another idea: introduce an object "index_expression" that can be
indexed to get an equivalent expression. Then
   i = index_expression[2:4,...]
   a[i]
would be equivalent to
   a[2:4,...]
There would be no new syntax to learn; although users might have
to know that index expressions are really tuples if they want
to do something that is not possible with standard indexing.

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Konrad Hinsen                     | E-Mail: hinsenk@ere.umontreal.ca
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