OpenEuphoria

Re: more match() problems

• Posted by Derek Parnell <ddparnell at bigpond.com> May 28, 2003
• 456 views

On Wed, 28 May 2003 07:43:20 +0000, Al Getz <Xaxo at aol.com> wrote:

>
>
> Hello again,
>
> Looking closer at the match() function,
> i find that it doesnt really work very well
> unless you are only using it on one level sequences (like {1,2,3} or 
> "abc").
>
> Untill this point, i dont think i ever used it
> for anything else, but since we were looking at it
> anyway i thought i would mention this.
>
> match({2,3},{1,2,3})
>
> returns the number 2, because the 'slice' was found
> in the second sequence.  Works fine.
>
> Now,
>
> match({{1,2,3}},{{1,2,3}})
>
> returns the number 1, because again the 'slice' (although this time 
> deeper) was found in
> the second sequence.  Works fine.
>
> Nowwwwwwwww...
>
> what does
>
> match({{2,3}},{{1,2,3}})
>
> return? (same example with the 1 missing in first arg)
>
> If you said the number 2, you are correct, because
> the 'slice' could be found in the second sequence
> at the required level, right???
>
> Well, guess again!
> The Eu match command returns a big fat zero!
>
> Yes, that's right,
>
> i=match({{1,2,3}},{{1,2,3}}) -- rets 1
> but
> i=match({{2,3}},{{1,2,3}}) -- rets 0
>
>
> Care to try to figure that out?

Sure. Let's look at all the possible slices of {{1,2,3}}, shall we.

 s = {{1,2,3}}
Length of s is 1, right?
 So then there is only one slice, namely s[1..1] and its value is 
{{1,2,3}}.

Now the LHS side of your match was {{2,3}}. Can you locate this value in 
any of the slices (all one of them) of s?


> I guess i went too far in assuming there was a method
> to the madness.
>
> Anomaly number 97316 and counting...

Not an anomaly at all. I keep saying this but it doesn't seem to be making 
it across the language barrier...

  match() LOOKS FOR SLICES - ALWAYS.
  find() LOOKS FOR ELEMENTS - ALWAYS.


-- 

cheers,
Derek Parnell