finding the position of a particular character in a string

deep3101 has asked for the wisdom of the Perl Monks concerning the following question:

I wanted to know if there is any method to find the position of occurance of a particular character in a string, the character can ofcourse occur more than once.

$a="THE FOOD IS DELICIOUS";
[download]

Then if I want the position of "O" so I should get 6,7,19 or 5,6,18 will work too. But don't want to use arrays and conventional

$pos++;

with for loop as the string is too big and lot of comparisons need to be done.

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Re: finding the position of a particular character in a string by NetWallah (Canon) on Oct 06, 2011 at 04:59 UTC
`>perl -e "my $a=q\|THE FOOD IS DELICIOUS\|;for(my $x=-1;($x=index($a,qq\| +O\|,$x+1))>=0;){print qq\|$x\n\|}" 5 6 18` [download] "XML is like violence: if it doesn't solve your problem, use more."	[reply] [d/l]
Re: finding the position of a particular character in a string by keszler (Priest) on Oct 06, 2011 at 03:29 UTC
`perl -E' $a="THE FOOD IS DELICIOUS"; $srch="O"; push @i,index($a,$srch,$i[-1]+1) for $a=~/$srch/g; $" = ","; say "@i"; ' 5,6,18` [download]	[reply] [d/l]
Re^2: finding the position of a particular character in a string by BrowserUk (Patriarch) on Oct 06, 2011 at 04:45 UTC
Searching twice is expensive and unnecessary: `$a="THE FOOD IS DELICIOUS";; $p=0; @p=(); push @p, $p-1 while $p = 1+index $a, 'O', $p; print @p;; 5 6 18` [download] Or: `$a="THE FOOD IS DELICIOUS";; @p=(); push @p, $-[0] while $a =~ m[O]g;; print @p;; 5 6 18` [download] Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l] [select]
Re: finding the position of a particular character in a string by ww (Archbishop) on Oct 06, 2011 at 08:28 UTC
deep3101: How did you arrive at "6,7,18 or 5,6,17" as acceptable results? `123456789012345678901 # one-based - 6,7,19 THE FOOD IS DELICIOUS 012345678901234567890 # zero-based - 5,6,18`	[reply]
Re^2: finding the position of a particular character in a string by deep3101 (Acolyte) on Oct 16, 2011 at 15:41 UTC
Instead of finding out my error you might as well have responded with a solution as others have. And from my end I extend apology for error in counting.	[reply]
Re^3: finding the position of a particular character in a string by Anonymous Monk on Oct 17, 2011 at 03:36 UTC
Instead of finding out my error you might as well have responded with a solution as others have. How , by reading your mind?	[reply]
Re^4: finding the position of a particular character in a string by deep3101 (Acolyte) on Nov 06, 2011 at 12:14 UTC
Re: finding the position of a particular character in a string by Anonymous Monk on Oct 06, 2011 at 03:18 UTC
perlfunc "Functions for SCALARs or strings " index, rindex ?node_id=3989;HIT=position%20%20string;re=N How can I find the first position of a substring case-insensitively?	[reply]