OpenEuphoria

Sequence of Suggestion (was Re: The Title Should At Least Mention Strings (was Re: Stupid Newbie-sounding q

• Posted by Pete Lomax <petelomax at blueyonder.co.uk> Jun 01, 2004
• 650 views

On Tue, 01 Jun 2004 11:16:22 +1000, Patrick Barnes
<mistertrik at hotmail.com> wrote:

>My view on this is:
>
>IT DOESN'T MATTER!
THEN CHANGE THE SUBJECT TITLE!  )

(scnr)

<snip>

>> >type textpict_line( sequence s)
>> >   if length(s) = 80 then return 1
>> >   else return 0
>> >   end if
>> >end type
>> >
>> >--2d array where the length of each line is fixed, and consists of
>> >characters
>> >sequence of textpict_line of char text_picture
>> >
>>One of the (deeply technical) problems I have with this approach is
>>that if text_picture[3] is updated, and textpict_line(text_picture[3])
>>returns true, should we then call char() 80 times? In the example you
>>post, yes, in general, no. (And it is the no case that should clearly
>>be pursued to enhance performance).
>
>So, what are we assigning to text_picture[3] ?
An expression. Think of what you might do with a text_picture. You
might invert all the characters for a blink effect, or slice and dice
to rotate, pan, or zoom the image. You might, for example, code
text_picture[3]=upper(text_picture[3]), or you might code
text_picture[3]=text_picture[3][2..80]&text_picture[3][1]

In both those cases, what is actually assigned is a function result
(upper() and concat()), which could be an object of any type, as far
as any non-sentient interpreter is concerned.

> If it's being assigned to 
>something that has the type textpict_line already, then we don't need to 
>type check the element, because it has already been type checked when it was 
>last changed.
That is very important, however allowing "<udt> of" ruins it:

type textpict_line( sequence s)
   if length(s) != 80 then return 0 end if
   return 1
end type

sequence of textpict_line of char text_picture

textpict_line somevar
	somevar=repeat({0,0},80)		-- OK
	text_picture[3]=somevar		-- Erm...

Here we assign a textpict_line to a textpict_line, so we don't need to
do any type checking right? Wrong, of course.

>I really think this would make Euphoria more flexible...
Oh, I'm not arguing against this, I think it would be good. Just
trying to nail down the details & quieten the grumbles in the back of
my head. I cannot prove it, but my gut feeling is that allowing a
second (or third..) "of" spanners it.

Pete
PS I am aware that defining somevar as a textpict_line of char will
solve the immediate problem.