| Re: Bug in SWITCH - ELSE: statement? [message #56307 is a reply to message #56306] |
Thu, 11 October 2007 09:42   |
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Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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Paul van Delst wrote:
> 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.
Ruby forces you to put it last:
#!/usr/bin/env ruby
number=ARGV[0].to_i
case number
else
puts("I don't like #{number}")
when 1..3
puts("#{number} is a good number")
end
lnx:scratch : ruby test_case.rb 5
test_case.rb:4: syntax error, unexpected kELSE, expecting kWHEN
test_case.rb:6: syntax error, unexpected kWHEN, expecting $end
when 1..3
^
In the right order it works as expected:
#!/usr/bin/env ruby
number=ARGV[0].to_i
case number
when 1..3
puts("#{number} is a good number")
else
puts("I don't like #{number}")
end
lnx:scratch : ruby test_case.rb 1
1 is a good number
lnx:scratch : ruby test_case.rb 5
I don't like 5
Ideally I would prefer the order to not matter, but if it does then I think IDL should
force the ELSE to be the last selector in CASE constructs (and probably SWITCH ones too)
cheers,
paulv
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