| Re: something like perl's 'require 5.4' [message #24698 is a reply to message #24696] |
Tue, 17 April 2001 09:05   |
Vapuser
Messages: 63
Registered: November 1998
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Member |
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JD Smith <jdsmith@astro.cornell.edu> writes:
> Craig Markwardt wrote:
>>
>> Vapuser <vapuser@catspaw.jpl.nasa.gov> writes:
>>> Hi all.
>>>
>>> I'm looking for something that check the version of the current IDL
>>> session against an input version, like perl's 'require 5.4'
>>> semantics and I *thought* I saw someone mention using something very
>>> much like this.
>>>
>>> Does anyone know of such a thing or was I just hallucinating?
>>
>> Extending on JD's answer with two more possibilities:
>>
>> if !version.release LT '5.4' then message, 'ERROR'
>> if double(!version.release) LT 5.4 then message, 'ERROR'
>>
>> The first comparison is a string compare, while the second one is a
>> numeric compare. There is a slight difference, but in practice they
>> are identical, and they also both handle the case of 5.4.1, etc. The
>> former will handle 5.4.1a, but I think it's rare. I always use the
>> latter.
>
> Hmmm...
>
> IDL> print,double('5.4') lt double ('5.4.1')
> 0
> IDL>print,double('5.4') eq double ('5.4.1')
> 1
>
> Hopefully RSI won't try to pull the latter on us.
>
> On the other hand, your string method looks good. The best counter
> example I could come up with is:
>
> IDL> print,'5.5a' lt '5.5B'
> 0
>
> Not too likely. I think I'll adopt the string version.
>
> Thanks,
>
> JD
How about:
version=strupcase(strjoin(strsplit(!version.release,'[.-_]', /extract), ""))
input_version=strupcase(strjoin(strsplit(desired_release,'[. -_]',/extract), ""))
if version lt input_version then 'eeek'
Clearly `desired_release' would have to be input as a string.
Of couse, this method 'requires' IDL 5.3 (IIRC), to get the regular
expression semantics of strsplit. The other question is will RSI use
any separator in version designations besides these three?
whd
--
William Daffer: 818-354-0161: William.Daffer@jpl.nasa.gov
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