[Jprogramming] if. do. elseif. else. end.

[Henry Rich]

select. in J is equivalent to a series of tests.  In fact there is some 
extra overhead, so it is used for explanatory value, not for 
performance.  It's nothing like a computed GOTO.

Henry Rich

On 12/11/2019 11:03 AM, 'Jim Russell' via Programming wrote:
> Yes but...
> I'd contend that a string of tests is usually less efficient than (perhaps calculating) some numeric value that is amenable to a case statement. ( I should have checked first; J does have a case statement, does it not?)
>
>> On Dec 11, 2019, at 10:32 AM, Henry Rich <henryhrich at gmail.com> wrote:
>>
>> Yes.
>>
>> Henry Rich
>>
>>> On 12/11/2019 5:46 AM, 'Mike Day' via Programming wrote:
>>> So is it still ok in J9 - and will it be ok - to continue using the following paradigm?
>>>
>>> if.     T  do. B
>>> elseif. T1 do. B1
>>> elseif. T2 do. B2
>>> end.
>>>
>>> Thanks,
>>>
>>> Mike
>>>
>>>
>>>> On 11/12/2019 10:23, Henry Rich wrote:
>>>> else. after elseif. is new in 9.01, and you found a bug in it.
>>>>
>>>> JfC is for J6.02.
>>>>
>>>> Henry Rich
>>>>
>>>> On 12/10/2019 8:23 PM, Ben Gorte wrote:
>>>>> Hi,
>>>>>
>>>>> Despite repeated warnings in JforC I stepped into the trap of using elseif.
>>>>> and else. in the same if.-statement. It took some effort to find that
>>>>> error, because the behaviour is kind of weird:
>>>>>
>>>>>    iftest =: 3 : 0
>>>>> if. y=1 do.
>>>>>     echo 'one'
>>>>> elseif. y=2 do.
>>>>>     echo 'two'
>>>>> elseif. y=3 do.
>>>>>     echo 'three'
>>>>> else. NB. should be elseif. do.
>>>>>     echo 'other'
>>>>> end.
>>>>> )
>>>>>
>>>>>      iftest 1
>>>>> one
>>>>> other
>>>>>      iftest 2
>>>>> two
>>>>> other
>>>>>      iftest 3
>>>>> three
>>>>>      iftest 4
>>>>> other
>>>>>
>>>>> Wouldn't it be possible to have that working like expected? Or elseif do
>>>>> flag an error?
>>>>>
>>>>> Greetings,
>>>>> Ben
>>>>> ----------------------------------------------------------------------
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