Re: A question about certain language features
-------Phoenix-Boundary-07081998-
Hi Derek Parnell, you wrote on 3/20/02 7:41:44 PM:
>I think that the primary reason for wanting to initialise variables when
>they are being
>declared is
>simply because it is convenient and reduces the chance of forgetting to do
>it. The current
>syntax
>for doing this only works outside of routines:
>
> integer x x = 5
> integer y y = 6
>
>the argument is that this is not a particularly pretty solution. For
>example:
>
> integer CustomerResidentialAddressIndex CustomerResidentialAddressIndex
>= 1
> integer CustomerMailingAddressIndex CustomerMailingAddressIndex = 1
>
My ?favorite? example of this kind of redundancy is something like:
CustomerResidentialAddressIndices = CustomerResidentialAddressIndices[2..
length (CustomerResidentialAddressIndices)]
An earlier fix I tried allowed the oddball syntax:
@foo[2..]
to be equivalent of:
foo = foo[2..length(foo)]
>Why not? It is inconsistent behaviour. I suggest it has been done this
>way just so that writing the interpreter was easier for RDS.
> I can not think of any other reason yet.
I think that the only reason for this can be because Rob wants it
that way.
It took me 2 months to add a dozen 'enhancements' to Eu, and most
of them were very easy once I understood the code sufficiently.
You have got to believe that Rob could add these features in a
week (maybe a month, with extensive testing).
>
>But real problem is the *initialisation* of variables
>and run-time control of that initialisation,
>Travis, in his article, explains the real problem,
>solved in Euphoria, not a problem of some individual taste.
>
I know its been here before, but could someone point me to this
article again?
>> > > 2) No support of call by reference. I understand that call
>> > > by reference can lead to unexpected side-effects, but since
>> > > changing global variables in a subroutine seems to
>> > > essentially cause the same problem, I don't understand this
>> > > omission.
As near as I can see, Pass By Reference involves a 'deep' change
to the language. Every modification to every passed variable
must check if the variable is a reference. This single extra
check would noticeably slow down all programs, violating a
prime design goal of Eu.
I partially implemented PBR and was surprised to find that
it slowed any program that did not use it extensively by
10-15%.
Karl Bochert
-------Phoenix-Boundary-07081998---
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