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how to substitute text - special case pauls 02-20-2008
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Posted by pauls on February 20, 2008, 5:54 pm
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 I have a text file in which I need to replace a plus sign surrounded by
spaces with just a single plus sign:

this:

ua = 1.5745e-09 + (3.3585e-09)*((temp+273.15)/(27+273.15)-1)**2

becomes:
ua = 1.5745e-09+(3.3585e-09)*((temp+273.15)/(27+273.15)-1)**2

I tried this:
s/ + /+/g;

But it did not seem to work...


Thanks, all help appreciated!!

P

Posted by A. Sinan Unur on February 20, 2008, 6:06 pm
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 YcgMiHanZ2dnUVZ_sytnZ2d@seanet.com:

> I have a text file in which I need to replace a plus sign surrounded
by
> spaces with just a single plus sign:
>
> this:
>
> ua = 1.5745e-09 + (3.3585e-09)*((temp+273.15)/(27+273.15)-1)**2
>
> becomes:
> ua = 1.5745e-09+(3.3585e-09)*((temp+273.15)/(27+273.15)-1)**2
>
> I tried this:
> s/ + /+/g;
>
> But it did not seem to work...

Well, I would venture to guess that it worked perfectly fine. The fact
that perl could not read your mind and change the meaning of characters
used in a regex to match your imagination does not imply that it did not
work.

Consulting the docs first is a far more productive way of solving
problems.

C:\> perldoc perlre

...

Quantifiers
The following standard quantifiers are recognized:
...
+ Match 1 or more times
...

So, the regex above matches one or more spaces followed by a space and
replaces such sequences with the plus sign.

C:\Temp> cat t.pl
#!/usr/bin/perl

use strict;
use warnings;

my $x = ' ' x 9 . ' - ' . ' ' x 1024;
$x =~ s/ + /+/g;

print "$x = $x\n";

C:\Temp> t
$x = +-+

It works! For even more fun, try

$x =~ s/ +? /+/g;

...

Now, to achieve what you want:

C:\Temp> cat t.pl
#!/usr/bin/perl

use strict;
use warnings;

my $x = q{1.5745e-09 + (3.3585e-09)*((temp+273.15)/(27+273.15)-1)**2};
$x =~ s/ \+ /+/g;

print "$x = $x\n";

C:\Temp> t
$x = 1.5745e-09+(3.3585e-09)*((temp+273.15)/(27+273.15)-1)**2


--
(remove .invalid and reverse each component for email address)
clpmisc guidelines: <URL:http://www.rehabitation.com/clpmisc.shtml>


Posted by John Bokma on February 20, 2008, 6:07 pm
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> I have a text file in which I need to replace a plus sign surrounded by
> spaces with just a single plus sign:
>
> this:
>
> ua = 1.5745e-09 + (3.3585e-09)*((temp+273.15)/(27+273.15)-1)**2
>
> becomes:
> ua = 1.5745e-09+(3.3585e-09)*((temp+273.15)/(27+273.15)-1)**2
>
> I tried this:
> s/ + /+/g;
>
> But it did not seem to work...

s/ \+ /+/g;

+ is a quantifier (1 or more) on the left side of the s///.

--
John

Arachnids near Coyolillo - part 1
http://johnbokma.com/mexit/2006/05/04/arachnids-coyolillo-1.html

Posted by lars on February 20, 2008, 6:07 pm
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pauls schrieb:
> I have a text file in which I need to replace a plus sign surrounded by
> spaces with just a single plus sign:
>
> this:
>
> ua = 1.5745e-09 + (3.3585e-09)*((temp+273.15)/(27+273.15)-1)**2
>
> becomes:
> ua = 1.5745e-09+(3.3585e-09)*((temp+273.15)/(27+273.15)-1)**2
>
> I tried this:
> s/ + /+/g;
>
> But it did not seem to work...
>
>
> Thanks, all help appreciated!!
>
> P

Try it this way

s/ \+ /\+/g

Posted by Gunnar Hjalmarsson on February 20, 2008, 6:23 pm
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lars wrote:
> Try it this way
>
> s/ \+ /\+/g
---------^
What's the reason for that backslash?

--
Gunnar Hjalmarsson
Email: http://www.gunnar.cc/cgi-bin/contact.pl

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