OpenEuphoria

Re: Short Circuit

• Posted by David Cuny <dcuny at LANSET.COM> Oct 06, 2000
• 769 views

I suspect that I had been a bit confusing in my initial post, so I'm going
to take another stab at this again.  No 'sequential or's in this post; I'll
try to restrict myself to real terms. I'll also be *much* less subtle,
sorry.

[ The Problem ]

Euphoria allows logical and comparison binary operators to return sequences.
For example:

   and
   or
   =

In the case of some operations, this is sensible. For example, the standard
math operators *should* with sequences. It makes sense to
add/subtract/multiply/divide two sequences.

The behavior of the '=', 'and' and 'or' is another matter entirely.

(1) The '=' comparison is worthless. You can only compare sequences that are
*exactly* the same in structure, with exactly the same lengths, down to the
last nested subsequence. I challange anyone to find me an example where this
is actually useful, other than for performing obscure tricks with bitmaps.

(Sorry, no prizes will be given to the winning entries.)


(2) Even if the behavior was useful, you *still* need to build a loop to
scan through the results. So instead of writing:

   s = ( s1 = s2 )
   for i = 1 to length( s ) do
      if s[i] then
         -- some code here
      end if
   end for

you could just as easily write:

   for i = 1 to length( s ) do
      if s1[i] = s2[i] then
         -- some code here
      end if
   end for

So there's no real benefit of returning the comparison results as a
sequence.

(3) The code shouldn't return an error. To be consistant (for example, with
'gets'), it should return an integer on failure, and a sequence on success.

(4) The '=' operator doesn't work the way people want it to. And, in the
end, the needs of the users should drive the design of the language, not the
other way around.

I've focused on the '=' operator, but similar arguments can be made for
changing the behavior of 'and' and 'or', with this additional argument:

(5) Short-circuiting should be consistant. It goes against the basic idea of
Euphoria (and simple consistancy) to have a keyword sometimes do one thing,
and sometimes do another.

[ The Solution ]

The solution is simple, and would break very little code. The result would
make Euphoria easier to use, more consistant, and less prone to errors. I
would think this would lead to More Happy Customers, which would be
beneficial to RDS.

(1) Change the behavior of '=' so it acts like 'equal'. It (and it's kin)
only return boolean integer values.

(2) Add the following functions to replace the old '=' behavior:

   compare_seq( o1, o2 )
   equal_seq( o1, o2 )

(3) Change 'and' and 'or' so they only accept integers, and only return
boolean integers.

(4) Add the following functions to replace the old functionality:

   and_seq( o1, o2 )
   or_seq( o1, o2 )

(5) Change short-circuiting so it always occurs.


Comments?

-- David Cuny