Re: Regexes and backslashes

If '\\n' (3 chars) is supposed to map to a single newline, what did you want '\n' to map to? '\n' (2 chars) or 'n'?

A hash isn't necessary if you use y///. I also wouldn't worry about the e modifier in this case. You are doing nothing more in the second half of substitution than what you would have to do anyway with an arbitrary string to untaint it: testing if it is defined and eliminating and substituting characters. These examples work with all one character backslash sequences (\t\n\r\f\b\a\e), not just newlines.

For '\n' to '\n' (2 chars):

  s /\\([^\\tnrfbae])|\\\\([tnrfbae])
    /(my$x=defined($1)?$1:$2)=~y#tnrfbae#\t\n\r\f\b\a\e#;$x;
    /gex;
[download]

For '\n' to 'n', this regex would do it:

  s /\\([^\\tnrfbae])|\\\\([tnrfbae])|\\([tnrfbae])
    /(my$x=defined($1)?$1:$2?$2:'')=~y#tnrfbae#\t\n\r\f\b\a\e#;$x?$x:$
+3;
    /gex;
[download]

Comment on Re: Regexes and backslashes Select or Download Code

Replies are listed 'Best First'.
Re^2: Regexes and backslashes by oko1 (Deacon) on Feb 17, 2011 at 00:09 UTC
> If '\\n' (3 chars) is supposed to map to a single newline, what did you want '\n' to map to? '\n' (2 chars) or 'n'? I don't want '\n' remapped at all. The only three things that I do want remapped are `\, \; \\n` - everything else should just be left as is. > A hash isn't necessary if you use y///. But I'm not trying to replace anything like a list of similar metacharacters. The whole challenge here is that I'm dealing with a set of things that are unlike each other: two sets of literal characters and one that is a literal plus a metacharacter. I'm just wondering if they can be handled by a common mechanism; that's what I'm asking about. Thank you for trying. -- Education is not the filling of a pail, but the lighting of a fire. -- W. B. Yeats	[reply]
Re^3: Regexes and backslashes by 7stud (Deacon) on Feb 17, 2011 at 03:56 UTC
To get a two character literal '\n' to convert to a newline "\n", which is not two characters,I think you have to use eval().	[reply]
Re^4: Regexes and backslashes by Anonymous Monk on Feb 17, 2011 at 04:05 UTC
No, its already been demonstrated that you don't have to use eval.	[reply]
Re^3: Regexes and backslashes by 7stud (Deacon) on Feb 17, 2011 at 03:56 UTC
To get a two character literal '\n' to convert to a newline "\n", which is not two characters, I think you have to use eval().	[reply]