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Re: Bug in SWITCH - ELSE: statement? [message #56308 is a reply to message #56307]

Thu, 11 October 2007 09:27

Paul Van Delst[1]
Messages: 1157
Registered: April 2002

Senior Member

Jean H wrote:
>> You brought up something interesting (to me anyway.) If you place
>> the
>> ELSE earlier in the SWITCH statement, then everything below it is
>> executed. If you do the same for a CASE statement then only then
>> ELSE is executed. It never occurred to me until I saw your post
>> that it was possible to place the ELSE anywhere but at the end.
>
> This is useless and can bring serious headaches...
>
> Both the Case and Switch run from the 1st condition to the last one...
> so anything you write below the "else" will never (Case) or always
> (Switch) be executed... then there is no need for a Case or Switch
> anymore! ... just delete (Case) your code or write it outside of the
> Switch block!

Goodness.... I never even thought of that. Why on Earth should the order of the case
selectors matter in a CASE construct? I just wrote:

pro test_case, number
case number of
else: print, 'I do not like this number!'
1: print, '1 is a good number'
2: print, '2 is even better'
3: print, '3 is weird looking'
endcase
end

IDL> .run test_case
% Compiled module: TEST_CASE.
IDL> test_case, 1
I do not like this number!
IDL> test_case, 3
I do not like this number!
IDL> test_case, 2
I do not like this number!
IDL> test_case,1000
I do not like this number!

That is just ridiculous behaviour.

The Fortran95 equivalent:

program test_case
integer :: number
write(*,'(/,"Enter a number:")',advance='no')
read(*,'(i10)') number

select case (number)
case default
write(*,*) 'I do not like this number!'
case (1:3)
write(*,*) number,' is a good number!'
end select

end program test_case

doesn not depend on the order of the "CASE"s:

lnx:scratch : lf95 --f95 test_case.f90
Encountered 0 errors, 0 warnings in file test_case.f90.
lnx:scratch : a.out

Enter a number:3
3 is a good number!
lnx:scratch : a.out

Enter a number:1000
I do not like this number!
lnx:scratch : a.out

Enter a number:2
2 is a good number!

that is what I would expect to happen. Seems like the IDL case construct cribs code from
the switch construct. Tsk tsk.

cheers,

paulv

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[Message index]

		Re: Bug in SWITCH - ELSE: statement? By: R.G.Stockwell on Fri, 12 October 2007 13:56
		Re: Bug in SWITCH - ELSE: statement? By: Matt[2] on Fri, 12 October 2007 13:40
		Re: Bug in SWITCH - ELSE: statement? By: JD Smith on Fri, 12 October 2007 12:43
		Re: Bug in SWITCH - ELSE: statement? By: R.G.Stockwell on Thu, 11 October 2007 09:47
		Re: Bug in SWITCH - ELSE: statement? By: Paul Van Delst[1] on Thu, 11 October 2007 09:42
		Re: Bug in SWITCH - ELSE: statement? By: Paul Van Delst[1] on Thu, 11 October 2007 09:27
		Re: Bug in SWITCH - ELSE: statement? By: larkn10 on Thu, 11 October 2007 08:39

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