OpenEuphoria

Re: [If/then and sequences...]

• Posted by Derek Parnell <derekp at solace.com.au> Aug 30, 2000
• 396 views

Hi Irv,
thanks for pointing this out.

In a lot of programming languages, the operators '<', '>' and '=' always
return a boolean result - that is either TRUE or FALSE. What you've
demonstated is that in Euphoria, these operators return a boolean when both
operands are atoms, and return a sequence when either operand is a sequence
(unless the operand is used in an IF statement, in which it is illegal). And
that compare() function always returns an atom (and equal() function always
returns a boolean), regardless of operands data type. In my mind that is
inconsistent and also not simple.

Its just that from my point of view, it would have been more intuitive, and
simpler, to reverse this arrangement of Robert's. That is, have the '<',
'>', and '=' operators always return a boolean (and allow their use in IFs),
and have the compare() function return a sequence. This probably would have
made the equal() function redunant. Of course its WAY too late to introduce
this sort of change to the language, and I'm not advocating that. I'm just
wondering why Robert decided to arrange the language the way he did.

To show it again...

Current:

 Operation      Operands      Allowed in IF       Result
-------------------------------------------------------------------
   =/>/<          atoms           yes               boolean
   =/>/<          sequences       no                sequence
   =/>/<          mixed           no                sequence
   compare()      atoms           yes               atom
   compare()      sequences       yes               atom
   compare()      mixed           yes               atom
   equal()        atoms           yes               boolean
   equal()        sequences       yes               boolean
   equal()        mixed           yes               boolean
   if             atom            yes               boolean
   if             sequence        no                n/a

Alternative:
 Operation      Operands      Allowed in IF       Result
-------------------------------------------------------------------
   =/>/<          atoms           yes               boolean
   =/>/<          sequences       yes               boolean
   =/>/<          mixed           yes               boolean
   compare()      atoms           no                sequence
   compare()      sequences       no                sequence
   compare()      mixed           no                sequence
   equal()        atoms           yes               boolean
   equal()        sequences       yes               boolean
   equal()        mixed           yes               boolean
   if             atom            yes               boolean
   if             sequence        no                n/a

-----
cheers,
Derek Parnell

>-----Original Message-----
>From: Derek Parnell [mailto:dparnell at bigpond.net.au]
>Sent: Wednesday, August 30, 2000 9:30 AM
>To: derekp at solace.com.au
>Subject: Re: [If/then and sequences...]
>
>
>On Tue, 29 Aug 2000, you wrote:
>> Agreed Matt. I'll never support a greater_than/less_than
>function. In fact,
>> I can't understand the rationale behind compare() and equal()
>either. To me,
>> it seems a lot more intuitive just to use the '=', '<', '>' symbols with
>> sequences. I can't understand Robert's idea that using these symbols with
>> sequences is a bad thing.
>>
>> So what's the big deal with ...
>>
>>  sequence A,B
>>
>>  if A = B then ....
>
>Run this little program, look at the output, and see why we might
>want  = to do
>what it does...
>
>sequence a,b
>a = {"Mary","Joe","Tim","Sue","Arnold"}
>b ={"Mary","Moe","Tom","Sue","Arnold"}
>
>? equal(a,b)
>? compare(a,b)
>? a = b
>
>--
>--Regards,
>--Irv
>