1. more match() problems
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?
I guess i went too far in assuming there was a method
to the madness.
Anomaly number 97316 and counting...
Take care,
Al
2. Re: more match() problems
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
3. Re: more match() problems
Derek Parnell wrote:
<snip>
> match() LOOKS FOR SLICES - ALWAYS.
> find() LOOKS FOR ELEMENTS - ALWAYS.
</snip>
This is entirely correct and is as it should be. I would further emphasize
that find() and match() only work at the top level.
Since match() always looks for slices, an atom as the first parameter is and
should be an error. An empty sequence as the first parameter is also an
error--a return of 0 is preferable, as it would eliminate some special case
checking from code using match().
-- Mike Nelson
4. Re: more match() problems
On Wed, May 28, 2003 at 02:47:51PM -0500, gertie at visionsix.com wrote:
<snip>
> I always do something like this:
>
> if atom(x)
> then z = match({x},y)
> else z = match(x,y)
> end if
>
> or
>
> if sequence(x)
> then z = match(x,y)
> else exit -- cannot use a goto eoroutine here!
> end if
>
> If i don't, sure as heck x will be "" eventually and the app will crash.
> Testing
> for equal(x,"") or (length(x) = 0 ) repeatedly, over and over, ad nauseum
> helps(?) too.
>
Why not:
function mx(object x, sequence s)
return match(x, s)
end function
global function match(object x, sequence s)
if atom(x) then
x = {x}
end if
if length(x) = 0 then
return 0
end if
return mx(x, s)
end function
That would get you almost exactly what you want, at the price of including one
more file into your program(s). No need to type repeatedly like that anymore ;]
> Kat
>
>
>
> TOPICA - Start your own email discussion group. FREE!
>
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5. Re: more match() problems
- Posted by gertie at visionsix.com
May 29, 2003
On 28 May 2003, at 20:11, jbrown1050 at hotpop.com wrote:
>
>
> On Wed, May 28, 2003 at 02:47:51PM -0500, gertie at visionsix.com wrote:
> <snip>
> > I always do something like this:
> >
> > if atom(x)
> > then z = match({x},y)
> > else z = match(x,y)
> > end if
> >
> > or
> >
> > if sequence(x)
> > then z = match(x,y)
> > else exit -- cannot use a goto eoroutine here!
> > end if
> >
> > If i don't, sure as heck x will be "" eventually and the app will crash.
> > Testing for equal(x,"") or (length(x) = 0 ) repeatedly, over and over, ad
> > nauseum helps(?) too.
> >
>
> Why not:
>
> function mx(object x, sequence s)
> return match(x, s)
> end function
> global function match(object x, sequence s)
> if atom(x) then
> x = {x}
> end if
> if length(x) = 0 then
> return 0
> end if
> return mx(x, s)
> end function
>
> That would get you almost exactly what you want, at the price of including one
> more file into your program(s). No need to type repeatedly like that anymore
> ;]
Nice, but there is overhead in function calls, and you make two of them.
Kat
6. Re: more match() problems
On Wed, May 28, 2003 at 08:43:21PM -0500, gertie at visionsix.com wrote:
<snip>
> Nice, but there is overhead in function calls, and you make two of them.
>
> Kat
>
That is true, but if that were the most important thing we'd all be programming
in assembler (or perhaps even in raw machine code!).
jbrown
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