| Ruby range operators? Re: IDL 8.0 compile_opt changes [message #69430 is a reply to message #69187] |
Fri, 08 January 2010 13:16   |
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Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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Maarten wrote:
> On Jan 7, 6:56 pm, mgalloy <mgal...@gmail.com> wrote:
>> I think we are agreeing here, but just to be sure: Python and IDL would
>> be specifying the endpoints of the range in the same way, it's just that
>> Python always includes the start index and excludes the end index (even
>> if not using negative indices):
>>
>>>> > a = [1, 2, 3, 4]
>>>> > a[1:3]
>> [2, 3]
>
> Yes. Although this is a fundamental difference that is the result of a
> choice both language developers made. Thinking about it a bit longer,
> I don't think the two can be made to act the same: IDL always includes
> the end index of the range, while Python always excludes it. Some
> emphasis on this in the documentation may be needed, as Python
> probably is the most widespread programming language that offers the
> facility of negative indices.
Well, since they're mucking about with operators in general, maybe ITTVIS could go the
ruby route and introduce the ".." and "..." range operators. The former is an inclusive
range (same functionality as ":") and the latter is a range that excludes the higher
value. So,
$ irb
irb(main)> a = [1,2,3,4,5,6]
=> [1, 2, 3, 4, 5, 6]
irb(main)> a[1..3]
=> [2, 3, 4]
irb(main)> a[1...3]
=> [2, 3]
irb(main)> a[1..-1]
=> [2, 3, 4, 5, 6]
irb(main)> a[1...-1]
=> [2, 3, 4, 5]
BTW, if IDL 8.0 will allow operator overloading, will it also allow for operator
definition? The overloading should allow for ".." having the same result as ":", but will
we be able to define functions/procedures that can be overloaded with "..." ?
cheers,
paulv
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