OpenEuphoria

RE: Changing Euphoria

• Posted by kbochert at ix.netcom.com Feb 04, 2002
• 408 views

-------Phoenix-Boundary-07081998-

Hi Shawn Pringle, you wrote on 1/31/02 9:37:11 AM:

>Ofcourse pass by reference is relatively cheap in EUPHORIA, being copy
>on write pointers.  It would seem to me that code like:
>list = append(list,a)  should be optimized to something like:
>append(!!list,a) keeping with your notation.  As, the object passed in
>will be reassigned there is no need to copy a new list in append.
>
>Apparently EUPHORIA already does this, at least for append.  The
>documentation says "highly optimized."
>

Built-in functions like append follow their own rules.
If the user writes a function that modifies one of it's
sequence parameters, the sequence is copied before
modification. If the user wants the modification AND a
return value, one or the other must be not passed to the
function or they must be combined into a sequence
(more copying!).
A third reason to add PBR (and slicing shorthands)
to Euphoria is to reduce redundancy:
I have read (and written) too many code lines like:
  MOD1_base_elements = doit (MOD1_base_elements[2..MOD1_base_elements])
Much better without the redundancy:
  doit (!!MOD1_base_elements[2..])

>As for object orientation, as you said, something like:
>      stack.push( 9 )
>would have to be stack = stack.push( 9 ), unless ofcourse we have
>stack=.push(9) for pass by reference like the other = ops.
>
>It may be pass by reference but we still only change things on the left
>side of the "=".
>

Generally, the method dispatch 'stack.push(9)' gets handled as
'push(stack, 9)' i.e. the instance to operate on is passed as a
a hidden parameter. Remember 'stack' here is an instance
(maybe of class STACK?) NOT a class!'.

In Euphoria this is:
  1) stack=push(stack,9)  -- push() can't return a value
or:
  2) push(stack,9)    -- stack must at file scope, or unchanged

We could make the rule that class methods can either return a value
OR modify the instance but I would rather make it more general,
especially when PBR brings other advantages.

-------Phoenix-Boundary-07081998---