| Re: Case statement question [message #42807] |
Wed, 23 February 2005 12:11 |
Mark Hadfield
Messages: 783
Registered: May 1995
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Senior Member |
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R.G.Stockwell wrote:
>
> NOTE: the
> commandstrings[12] = 'do_elsedefault()'
> takes advantage of IDLs array overrun "feature" where any x
> gt 11 will call that last element (thereby reproducing the effect of the
> "else" statement in the case command).
You really like living on the edge, don't you Bob?
--
Mark Hadfield "Ka puwaha te tai nei, Hoea tatou"
m.hadfield@niwa.co.nz
National Institute for Water and Atmospheric Research (NIWA)
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| Re: Case statement question [message #42817 is a reply to message #42807] |
Wed, 23 February 2005 09:19  |
R.G.Stockwell
Messages: 163
Registered: October 2004
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Senior Member |
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"Paul Van Delst" <paul.vandelst@noaa.gov> wrote in message
news:cvib57$7n3$1@news.nems.noaa.gov...
>> How about
>>
>> switch x of
>> 0: do_this() & break
>> 1:
>> 2:
>> ...
>> 9: do_that() & break
>> 10: do_something_else() & break
>> 11: do_something_more() & break else: whatever()
>> endswitch
>
> Oooo - I prefer this to the solution I posted. Looks cleaner.
I disagree with you Paul, I like your solution best.
In fact I was about to post a response, and then saw yours, and
sent my inelegant solution to the intergalactic bitbucket in the sky.
I don't think the above is really any different than the original question
(it is easy to paste do_that(x) 10 times.)
> Of course, I prefer the Fortran solution above all:
> SELECT CASE (x)
> CASE (0); do_this()
> CASE (1:9); do_that(x)
COOL!
How about something along the lines of:
commandstrings = strarray(12)
commandstrings[0] = 'do_this()'
commandstrings[1:9] = 'do_that(x)'
commandstrings[10] = 'do_something_else()'
commandstrings[11] = 'do_something_more()'
commandstrings[12] = 'do_elsedefault()'
r = execute(commandstring[x])
NOTE: the
commandstrings[12] = 'do_elsedefault()'
takes advantage of IDLs array overrun "feature" where any x
gt 11 will call that last element (thereby reproducing the effect of the
"else" statement in the case command).
Cheers,
bob
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| Re: Case statement question [message #42818 is a reply to message #42817] |
Wed, 23 February 2005 08:32 |
Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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Michael Wallace wrote:
>> case 1 of
>> (x eq 0): do_this()
>> (x ge 1 and x le 9 ): do_that(x)
>> (x eq 10): do_something_else()
>> (x eq 11): do_something_more()
>> else: message, "Error!"
>> endcase
>
>
> Sweet! That works. I would have never thought to switch the logic
> around such that you're sending "true" into the case and looking for the
> case that evaluates to "true." I guess every example I've seen has been
> one where you send in the value you want to find, not the truth value
> you want to find. Wow. Can you tell that I'm easily amused by
> programming logic? Or maybe it's the caffeine talking. ;-)
I think it's the caffiene. :o)
Don't attribute any programming smarts to me - that example is straight out of the docs.
paulv
--
Paul van Delst
CIMSS @ NOAA/NCEP/EMC
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| Re: Case statement question [message #42819 is a reply to message #42818] |
Wed, 23 February 2005 08:31 |
Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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Benjamin Hornberger wrote:
> Michael Wallace wrote:
>
>> case x of
>> 0: do_this()
>> 1: do_that(x)
>> 2: do_that(x)
>> 3: do_that(x)
>> 4: do_that(x)
>> 5: do_that(x)
>> 6: do_that(x)
>> 7: do_that(x)
>> 8: do_that(x)
>> 9: do_that(x)
>> 10: do_something_else()
>> 11: do_something_more()
>> endswitch
>>
>> Is there a way to group 1 - 9 into a single expression rather than
>> having to list each distinct number in the range?
>>
>> -Mike
>
>
> How about
>
> switch x of
> 0: do_this() & break
> 1:
> 2:
> ...
> 9: do_that() & break
> 10: do_something_else() & break
> 11: do_something_more() & break
> else: whatever()
> endswitch
Oooo - I prefer this to the solution I posted. Looks cleaner. Of course, I prefer the
Fortran solution above all:
SELECT CASE (x)
CASE (0); do_this()
CASE (1:9); do_that(x)
CASE (10); do_something_else()
CASE (11); do_something_more()
CASE DEFAULT; whatever()
END SELECT
And you can do stuff like
CASE (:-1)
to specify any negative numbers or
CASE (1:)
to specify any positive numbers. And multiple single/ranges too:
CASE (1, 3, 7:10, 13, 15:20)
Very bloody handy.
Personally I think IDL should've used different syntax for the CASE/SWITCH constructs. I
would prefer something more like the Fortran example above:
case x of
0) do_this()
1:9) do_that(x)
10) do_something_else()
11) do_something_more()
else) whatever()
endcase
so you could use ":" to specify ranges.
paulv
--
Paul van Delst
CIMSS @ NOAA/NCEP/EMC
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| Re: Case statement question [message #42831 is a reply to message #42819] |
Tue, 22 February 2005 15:57 |
Mark Hadfield
Messages: 783
Registered: May 1995
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Senior Member |
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David Fanning wrote:
> Michael Wallace writes:
>
>> case x of
>> 0: do_this()
>> 1: do_that(x)
>> 2: do_that(x)
>> 3: do_that(x)
>> 4: do_that(x)
>> 5: do_that(x)
>> 6: do_that(x)
>> 7: do_that(x)
>> 8: do_that(x)
>> 9: do_that(x)
>> 10: do_something_else()
>> 11: do_something_more()
>> endswitch
>>
>> Is there a way to group 1 - 9 into a single expression rather than
>> having to list each distinct number in the range?
>
> I can't tell if this is too obvious or I'm being dense:
>
> case x of
> 0: do_this()
> 10: do_something_else()
> 11: do_something_more()
> else: do_that(x)
> endcase
Another you might not have thought of:
case 1B of
(x ge 0) and (x le 9): do_that(x)
x eq 10: do_something_else()
x eq 11: do_something_more()
else: crash_and_burn
endcase
It's a bugger to indent, though.
--
Mark Hadfield "Ka puwaha te tai nei, Hoea tatou"
m.hadfield@niwa.co.nz
National Institute for Water and Atmospheric Research (NIWA)
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| Re: Case statement question [message #42832 is a reply to message #42831] |
Tue, 22 February 2005 15:51 |
Benjamin Hornberger
Messages: 258
Registered: March 2004
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Senior Member |
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Michael Wallace wrote:
> case x of
> 0: do_this()
> 1: do_that(x)
> 2: do_that(x)
> 3: do_that(x)
> 4: do_that(x)
> 5: do_that(x)
> 6: do_that(x)
> 7: do_that(x)
> 8: do_that(x)
> 9: do_that(x)
> 10: do_something_else()
> 11: do_something_more()
> endswitch
>
> Is there a way to group 1 - 9 into a single expression rather than
> having to list each distinct number in the range?
>
> -Mike
How about
switch x of
0: do_this() & break
1:
2:
...
9: do_that() & break
10: do_something_else() & break
11: do_something_more() & break
else: whatever()
endswitch
Benjamin
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| Re: Case statement question [message #42833 is a reply to message #42832] |
Tue, 22 February 2005 15:50 |
Michael Wallace
Messages: 409
Registered: December 2003
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Senior Member |
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> case 1 of
> (x eq 0): do_this()
> (x ge 1 and x le 9 ): do_that(x)
> (x eq 10): do_something_else()
> (x eq 11): do_something_more()
> else: message, "Error!"
> endcase
Sweet! That works. I would have never thought to switch the logic
around such that you're sending "true" into the case and looking for the
case that evaluates to "true." I guess every example I've seen has been
one where you send in the value you want to find, not the truth value
you want to find. Wow. Can you tell that I'm easily amused by
programming logic? Or maybe it's the caffeine talking. ;-)
-Mike
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| Re: Case statement question [message #42834 is a reply to message #42833] |
Tue, 22 February 2005 15:44 |
Michael Wallace
Messages: 409
Registered: December 2003
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Senior Member |
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David Fanning wrote:
> Michael Wallace writes:
>
>
>> case x of
>> 0: do_this()
>> 1: do_that(x)
>> 2: do_that(x)
>> 3: do_that(x)
>> 4: do_that(x)
>> 5: do_that(x)
>> 6: do_that(x)
>> 7: do_that(x)
>> 8: do_that(x)
>> 9: do_that(x)
>> 10: do_something_else()
>> 11: do_something_more()
>> endswitch
>>
>> Is there a way to group 1 - 9 into a single expression rather than
>> having to list each distinct number in the range?
>
>
> I can't tell if this is too obvious or I'm being dense:
>
> case x of
> 0: do_this()
> 10: do_something_else()
> 11: do_something_more()
> else: do_that(x)
> endcase
>
It is too obvious! :-) I already have an else block statement in my
case which I didn't include in my example. My bad for leaving it out.
And if you notice, I made a second mistake by ending my case with an
endswitch. I'm getting loopy from all this IDL.
-Mike
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| Re: Case statement question [message #42835 is a reply to message #42834] |
Tue, 22 February 2005 15:37 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Michael Wallace writes:
> case x of
> 0: do_this()
> 1: do_that(x)
> 2: do_that(x)
> 3: do_that(x)
> 4: do_that(x)
> 5: do_that(x)
> 6: do_that(x)
> 7: do_that(x)
> 8: do_that(x)
> 9: do_that(x)
> 10: do_something_else()
> 11: do_something_more()
> endswitch
>
> Is there a way to group 1 - 9 into a single expression rather than
> having to list each distinct number in the range?
I can't tell if this is too obvious or I'm being dense:
case x of
0: do_this()
10: do_something_else()
11: do_something_more()
else: do_that(x)
endcase
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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| Re: Case statement question [message #42836 is a reply to message #42835] |
Tue, 22 February 2005 15:35 |
Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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Michael Wallace wrote:
> case x of
> 0: do_this()
> 1: do_that(x)
> 2: do_that(x)
> 3: do_that(x)
> 4: do_that(x)
> 5: do_that(x)
> 6: do_that(x)
> 7: do_that(x)
> 8: do_that(x)
> 9: do_that(x)
> 10: do_something_else()
> 11: do_something_more()
> endswitch
>
> Is there a way to group 1 - 9 into a single expression rather than
> having to list each distinct number in the range?
case 1 of
(x eq 0): do_this()
(x ge 1 and x le 9 ): do_that(x)
(x eq 10): do_something_else()
(x eq 11): do_something_more()
else: message, "Error!"
endcase
?? I think the syntax is correct, but I'm not sure.
paulv
--
Paul van Delst
CIMSS @ NOAA/NCEP/EMC
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