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strpos - how to deal with numbers and separators?
Posted: 22 Aug 2012 18:23
by tiago
hi guys.
is there a way i could do this?
echo strpos("1,111,11", "11", , , ","); // 3 - reported by separator
currently it reports "2", which is false anyway (ok, true in the context of current implementation, but false for the situation I need to deal with, ie, reporting the occurrence of the absolute "11" and not the first '11').
Re: strpos - how to deal with numbers and separators?
Posted: 22 Aug 2012 18:50
by highend
which is false anyway
No, this is false...
2 is correct, because the first token is referenced by 0, not 1.
Re: strpos - how to deal with numbers and separators?
Posted: 22 Aug 2012 18:57
by tiago
"false for the situation I need to deal with", not the returned value...
Re: strpos - how to deal with numbers and separators?
Posted: 22 Aug 2012 19:09
by highend
and the situation you have to deal with is?
Just add +1 to the return value and you're good to go?
Re: strpos - how to deal with numbers and separators?
Posted: 22 Aug 2012 19:19
by tiago
No, I need strpos to return the position (first occurrence) of a exact value assuming there's a separator between them.
If the exact value isn't there, then report "-1".
echo strpos("1,111,11111", "11", , , ","); // -1
-currently reports '2'...
Re: strpos - how to deal with numbers and separators?
Posted: 22 Aug 2012 19:48
by highend
Code: Select all
$search = "11111";
$a = "1,111,11111,1111111";
$i = 1;
foreach($number, $a, ",") {
$token = gettoken($a, $i, ",");
if($token == $search) {
$found = $i;
break;
} else {
$found = -1;
}
$i++;
}
msg "Position is: " . $found;
Not very elegant but does it's job...
Re: strpos - how to deal with numbers and separators?
Posted: 22 Aug 2012 19:56
by tiago
Yes, I did something like that which turned out to be very cpu intensive.
Strpos is astonishingly faster and that's why I asked for such implementation.
Re: strpos - how to deal with numbers and separators?
Posted: 22 Aug 2012 22:11
by PeterH
Add a separator, i.e. "," to start and end of haystack and of needle, and try!
Code: Select all
echo strpos(",1,111,11,", ",11,", , , ",");
Does this help?
Re: strpos - how to deal with numbers and separators?
Posted: 24 Aug 2012 01:00
by tiago
Because
echo strpos(",1,111,11111,11", ",11,", , , ","); // -1
-why not a simple solution for this? It does make sense, it's already implemented in other incarnations of commands, and anything else is making an easy task harder. sigh
Re: strpos - how to deal with numbers and separators?
Posted: 24 Aug 2012 10:03
by PeterH
tiago wrote:Because
echo strpos(",1,111,11111,11", ",11,", , , ","); // -1
-why not a simple solution for this? It does make sense, it's already implemented in other incarnations of commands, and anything else is making an easy task harder. sigh
It seems you missed a "," at the end of the 1st parm?
In a form usable inside a program:
Code: Select all
$var = "1,111,11111,11";
$num = "11"; // this number might be unquoted
$sep = ",";
echo strpos($sep.$var.$sep, $sep.$num.$sep, , , $sep); // 12
The returned number might be corrected by -1 
Edit: maybe some explanation:
StrPos() relates to strings. What you are looking for would be something like "TokenPos()"...
But if you are looking for a (better: for the first) matching
delimited token in a string you can basically search for that token by adding the token delimiters, i.e. ",11," for token "11" - so I added the 2 delimiters for the second operand in my code.
Sure this wouldn't function with the first or last token - both miss one delimiter. You can help by adding these delimiters to the first parameter. Now every token is inside delimiters.
Advantage: avoid a loop, simple code.
I was wrong with the hint of correcting the result by -1
the search string is prefixed by a delimiter, (i.e. 1 char is added,) but the match is on the leading search-delimiter, not on the first char of the search token, so 1 char is subtracted again
Re: strpos - how to deal with numbers and separators?
Posted: 31 Aug 2012 19:33
by tiago
Yes, you got it.
Now and then I face problems like this so a TokenPos would be a more than ideal solution.
Just posted another related question such TokenPos may cover.
Let's pray...