On May 22, 2009, at 12:56 PM, Dijk van Marc wrote:
A PDB file is essentially a table. One line from such a table can be
ATOM 14 CA GLN A 2 -27.648 -9.581 30.325 1.00 10.00
In the language description I would like to use a regular expression
matched 'GLN' only if the line starts with either 'ATOM' or
'HETATM'. This seams like
a conditional regular expression but my attempts to implement it at
such have failed
Start a begin/end match with a look-ahead on ATOM|HETATM:
And an end of $ (end of line). Inside the pattern rules have a match
for the GLN.
You could use a conditional regex to do this if it was before the
ATOM, but you can't do look-behinds of an unspecified length.