OpenEuphoria

Re: Strings and the like.

• Posted by Everett Williams <rett at GVTC.COM> Dec 08, 1999
• 521 views

My apologies, but somehow, I sent this previously incomplete. This is the
full text.

Lucius L. Hilley III wrote:

>    What if something like these were built-in?
>
>-----------------------------------
>type whole_number_set(sequence s)
>  for A = 1 to length(s) do
>    if (s[A] = floor(s[A])) then
>      return 0
>    end if
>  end for
>
>  return 1
>end type
>-----------------------------------

I think that you have a small error in these routines, and I would not
see the difference between your's and this:

type whole_number_set(sequence s)
 sequence temp1
 temp1 =  (s = floor(s))
 return (find(0, temp) = 0)
 end type
-----------------------------------
>
>Then you would be able to specify any range and test it
>effeciently such as a byte_set() below.  Of course, these
>sets are enforcing that you have a one dimensional sequence.
>But that is the whole point of detecting strings.
>
>-----------------------------------

and this

type byte_set(sequence s) -- I.E.: standard ASCII byte STRING !!!
  sequence temp
 if whole_number_set(s) then
    temp = ((s >= 0) and (255 > s))
    return (find(0, temp) = 0)
  end if
end type

Are you deliberately leaving xFF out of the set?

Anyway, I think I recognize a palliative gesture here. You have described a
very specific, very non-embedded Euphoria typing routine here. It appears
that the only way to type check by these techniques is to check the
entire sequence each time that any operation is made on the sequence...
OUCH!!...can anybody spell overhead. The only way to prevent this would
be to assign the substring to be affected to another type-checked variable
before the operation and then assign it back. Not only would this be
clumsy, in some cases it might be tricky and from what I can tell, it would
trigger the type check anyway on the whole string. Depending on how often
the test is triggered for operations that affect the whole or some slice of the
string, this could get ugly.

OUCH!!...I, as an Euphoria newby, just stomped on a really ugly artifact of
Euphoria and sequences. I see how relational and logical operators produce
multiple results, true values rather than logical values. A logical value is a
temporary item that only exists at the point of comparison unless
deliberately and separately preserved. Unless the comparands are also
preserved, any such logical "value" loses its relevance as soon as those
comparands lose their validity. For validity, where a single logical result is
expected, Euphoria should sequentially "and" together the truth values
for this purpose. This should be valid, for example:

type whole_number_set(sequence s)
 return (s = floor(s))
end type

And in any other case where a single value would be necessary for
consistency.  Another example would be:

sequence s
s = "ABCD"
if s = floor(s) then ....

end if

This is a major logical hole in the language. There needs to be a clear
distinguishing between relational and logical symbols as functional
operators returning a value or values and those same operators as
standard truth tests in our standard binary logic system. Neither mode
needs to be excluded. Overloading is not a problem here...I don't think.
Maybe somebody can come up with a counter to that thought.

Everett L.(Rett) Williams
rett at gvtc.com