in reply to Replacing characters in a line

Hi, just try this,

$string='ATOM   3316  N   TYR D  24      97.479  18.805   2.990  1.00 
+36.32      D    N 
ATOM   3322  CD1 TYR D  24      96.225  15.974   2.812  1.00 17.96    
+  D    C';

$string=~s#((\w+)   \d{4}  \w   TYR )D#$1X#gsi;

print $string;

output:
*******
ATOM   3316  N   TYR X  24      97.479  18.805   2.990  1.00 36.32    
+  D    N
ATOM   3322  CD1 TYR D  24      96.225  15.974   2.812  1.00 17.96    
+  D    C

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Re^2: Replacing characters in a line
by holli (Abbot) on Mar 04, 2005 at 12:45 UTC
    Why not just s/(?<=TYR )D/X/;?

    Update:
    Or, to keep it fixed-length: 
    s/^(.{21})D/$1X/;

    [download]

    Sidenote:
    Has anyone an idea, why this: 
    s/^(?<=.{21})D/X/;

    [download]
    does not work, while this 
    s/(?<=.{21})D/X/;

    [download]
    does (but donīt use this, itīs unsafe)?


    holli, /regexed monk/
[reply]
[d/l]
[select]
      Are we sure that D will always be preceeded by "TYR " ??
      Manav
[reply]
        We can only tell from the example data.
        pelagic's regex is also unsafe. what if the line looks like 
        ATOM   3316  N   TYR B  24      97.479  18.805   2.990  1.00 36.32    
+  D    N

        [download]
        Then the alone "D" at the end will be replaced by "X". Intended??

        I would use the substr()-solution above. My regex was just meant as an optimization of perlsen's one, which is unneccesary complicated.

        Update:
        Striked the sillyness about the second "D".
        /me writes "Must read the question properly" 200 times.


        holli, /regexed monk/
[reply]
[d/l]
        We are not!
        As the OP stated: there are two D's on every line.

        pelagic
[reply]

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