OpenEuphoria

Re: ESL Master Include File

• Posted by Pete Lomax <petelomax at blueyonder.co.uk> Jul 26, 2005
• 540 views

On Mon, 25 Jul 2005 19:24:24 -0700, Derek Parnell
<guest at RapidEuphoria.com> wrote:

>Pete Lomax wrote:
>
>[snip]
>> Despite the highly unlikely chance 
>> of such things, some libraries actually do define TRUE=(1=1) and
>> FALSE=(1=0).
>
>That would be me 
>
>> There is nothing wrong with using tri-logic with say isTLtrue=1, 
>> isTLunknown=0, and isTLfalse=-1, (though isTLfalse=0, and 
>> isTLunknown=-1 would probably be just as effective) but 
>> defining FALSE as -1 is just brain-dead stupidity.
>
>Why? The only requirement is that TRUE and FALSE have different values from
>each other.

What about code readability? In the following example, if the
commented out lines are used instead of the line after them, it
functions exactly the same:

constant FALSE=-1, TRUE=1

function e(integer a, integer b)
-- integer-only version of equal()
--	return a=b
	if a=b then return TRUE else return FALSE end if
end function

--	if e(1,1)=TRUE then
	if e(1,1) then
		-- because TRUE was defined sensibly, this happens
		puts(1,"1 is equal to 1\n")
	else
		puts(1,"1 is NOT equal to 1\n")
	end if

--	if e(1,0)=FALSE then
	if not e(1,0) then
		puts(1,"1 is not equal to 0\n")
	else
		-- because FALSE was defined wrong, this happens.
		puts(1,"1 is !!EQUAL!! to 0\n")
	end if

> One could have ...
>
>constant  TRUE  = 't',
>          FALSE = 'f'
>
.. And one could have
constant TRUE = {"banana","grandmother","waspsting"},
		FALSE = not TRUE

>And all code that relied on using TRUE and FALSE would still work. 
Possibly, but there is certainly a much higher potential for error.
The example above works if you consistently use TRUE=1 and FALSE=-1,
but shows how easy it would be to slip and fall.

If you are going to have a global constant, it must adhere to the
principle of least astonishment.

Presumably, by the warped logic occurring in this thread, if 
constant EOF="the end" is defined then getc() should analyse
the program source, figure out what it is going to be tested
against, and return -1 or "the end" appropriately? Maybe the same
could be said for equal() and FALSE. I am being silly, of course.

>BTW, and I'm sure you already know this, but there are plenty of languages that
>implement TRUE as -1 instead of 1.
And it would be equally wrong in such languages to define a global
constant of TRUE as +1.

Regards,
Pete