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Home: Perl Programming Help: Regular Expressions:
How to change [1,2,3] to [1][2][3]

tacallah
New User

Feb 11, 2009, 6:31 AM

Post #1 of 5 (8256 views)

How to change [1,2,3] to [1][2][3]	Can't Post

I am trying to write a regular expression to do the following:

[#,#,#] => [#][#][#]
[ # , # , # ] => [#][#][#]

Here is what I have tried:

my $x = "[3,4,5]\n[ 3 , 4 , 5 ]\n";
print "BEFORE\n$x";
$x =~ s/(?<=\[)\s*(\d+)\s*,/$1][/g;
print "AFTER\n$x";

>>> OUTPUT <<<
BEFORE
[3,4,5]
[ 3 , 4 , 5 ]
AFTER
[3][4,5]
[3][ 4 , 5 ]

The following will work by using a while loop:

my $x = "[3,4,5]\n[ 3 , 4 , 5 ]\n";
print "BEFORE\n$x";
while ($x =~ s/\[\s*(\d+)\s*,/[$1][/g) {}
$x =~ s/\[\s*(\d+)\s*\]/[$1]/g;
print "AFTER\n$x";

>>> OUTPUT <<<
BEFORE
[3,4,5]
[ 3 , 4 , 5 ]
AFTER
[3][4][5]
[3][4][5]

Is there any way to this with a single substitute?

Thanks!

KevinR
Veteran

Feb 11, 2009, 4:06 PM

Post #2 of 5 (8246 views)

Re: [tacallah] How to change [1,2,3] to [1][2][3] [In reply to]	Can't Post

Code

my $x = "[3,4,5]\n[ 3 , 4 , 5 ]\n"; 
$x =~ s/([\[,]?)\s*(\d+)\s*([,\]]?)/[$2]/g; 
print $x;

-------------------------------------------------

tacallah
New User

Feb 11, 2009, 9:00 PM

Post #3 of 5 (8239 views)

Re: [KevinR] How to change [1,2,3] to [1][2][3] [In reply to]	Can't Post

Thanks for your reply. Your solution does work for the string which I gave, but it could produce wrong results:

[1] 2 [3] => [1][2][3]
1, 2, 3 => [1][2][3]
<1> has 1 inside. => <[1]> has[1]inside.

I appreciate your effort. I am hoping to find a regular expression that only changes numbers enclosed within square brackets.

KevinR
Veteran

Feb 11, 2009, 10:28 PM

Post #4 of 5 (8233 views)

Re: [tacallah] How to change [1,2,3] to [1][2][3] [In reply to]	Can't Post

In Reply To

OK.
-------------------------------------------------

1arryb
User

Feb 26, 2009, 1:58 PM

Post #5 of 5 (8146 views)

Re: [KevinR] How to change [1,2,3] to [1][2][3] [In reply to]	Can't Post

Kevin,

or, more simply:

Code

my $x = "[3,4,5]\n[ 3 , 4 , 5 ]\n";  
$x =~ s/,/][/g; 
$x =~ tr/ //d;  
print $x;

It takes a second scan to trim the white space (should that prove necessary, but it's sure easier to understand Laugh

UPDATE:

D'oh! We both forgot the '1, 2, 3' case:

Code

my @xs = ('[3,4,5]', '[ 3 , 4, 5 ]', '3 , 4 , 5');  
for my $x (@xs) { 
    $x =~ s/[\[\] ]//g;   # normalize all variants to '3,4,5'. 
    $x =~ s/,/][/g; 
    print "[$x]\n"; 
}

Cheers,

Larry

(This post was edited by 1arryb on Feb 26, 2009, 2:09 PM)

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