RE: match() (not short, he he)
>Kat wrote:
>
>Yes, strangely enough, i have other ideas. 
>
>i'd prefer
>
>match('a',"something")
>
>to not fail because of the alledgedly abhorent reason that 'a' isn't a
>sequence.
>It's too late to change, but i'd prefer
>
>match('a',"kat")
>
>to return 2, since the 'a' in "kat" is an atom. And
>
>match("b",{"a",'b',"b","c"})
>to return 3, because the third element "b" in the second parameter of
>match
>is a sequence, and the 2nd parameter isn't. I haveto test parms in
>match() for
>that first parm being a sequence all the time too.
>
>Kat
>
Hello again Kat,
I dont think any of your ideas have been strange, rather,
i think they hint on what all Euphoria users want in the
language in one form or another.
I dont think i made it quite that clear why i was saying
match("b",{"a","b","c"})
should return 0 and not the number 3 though.
The main reason is that match now returns a single number,
which is a single dimensional quantity. The reason it has
to be single dimensional is because match works on only
one level of the sequence at a time. The level it searches
in the second sequence is always the same as the level
of the first sequence. It has to be this way, or else we
wouldnt know where it was looking, and the number it returned
would be meaningless to us.
A simple example:
match("b",{"abc"})
match("b",{"a","b","c"})
match("b",{"ab","c","d"})
match("b",{{"a","b","c"}})
These cant all return the number 2, can they?
To find out, all we have to do is try using the
proposed new results in a program and see what happens.
In the following code, all i have done is forced match
to return the number 2 for every case which i 'think'
you want to see the number 2 returned. I did this
simply by setting i=2 AFTER the match calls.
By inspecting these results below, you will see that
there is only one case where match truely returns
the number 2, and it does appear to be correct.
Let's try these one at a time and see...
[1]
s="abc"
i=match("b",s) --returns 2
i=2
?s[i] --prints >98< --works fine!
[2]
s={"a","b","c"}
i=match("b",s) --returns 0
i=2
?s[i] --prints >{98}< --is this correct?
[3]
s={"ab","c","b"}
i=match("b",s) --returns 0
i=2
?s[i] --prints >{99}< --this is clearly incorrect!
[4]
s={{"a","b","c"}}
i=match("b",s) --returns 0
i=2
?s[i] --subscript value 2 is out of bounds, reading from a sequence of
length 1
Nobody seems to be saying that #1 above isnt correct, and that is
the only one that works correctly, really. match returns 2 anyway.
In #2, match returns 0 and when we force it to be a 2 we end
up printing the correct number, 98, but it's inside of a sequence.
Arguably, this may be interpreted to be correct in some cases, but
in #3, when we apply the same idea, we get a totally incorrect
result, as now we end up printing the number 99 inside a sequence,
which is totally wrong. We end up printing the 'c' instead of what
we were really looking for, the 'b'.
in #4, we get really bad results, but again it is arguable that
?s[i] with i=0 would have done the same thing. This says that
our code has to be able to handle the possibility of match returning
a zero, but we still havent found the "b" nested inside of s in this
example, so this fails also.
The reason why some of these tests fail and some return incorrect
results is because match, right now, only returns a single number.
If match could return a sequence, this would change and what you
want to do would work.
Repeating #4 allowing match to return a sequence:
[4r]
s={{"a","b","c"}}
i=match("b",s) --returns 0
ss={1,2,1} --'force' match to return sequence
--now let's use this sequence to try to print the b:
?s[ss[1]][ss[2]][ss[3]] --prints >98< --yeahhh!
Finally, we found the correct value within {{"a","b","c"}}
but it took three dimensions to do it.
Granted this would work, but match would have to be
seriously updated 
Also, once found, it would be hard as heck to find the
next occurance of "b" wouldnt it? Try that
match() would also have to be updated to accept a
starting point in the sequence, something i have
always wanted in "find()". That's another story though
------->
All i was asking for is that match to return a zero when
the first sequence is null "" (exactly) with no regard
for the second sequence. Without this, we can never
use the following line in our code:
while match(s1,s2) do
for fear that s1 might become the null sequence at some point,
as in:
while match(s1,s2) do
--reduce length of s1 and do other stuff
end while
Take care for now,
Al
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