Parsing regular expressions differently - feature request
Wacek Kusnierczyk wrote:
Duncan Murdoch wrote:
That might solve John's problem, but I doubt it. As far as I can see
it won't handle \L, for example.
well, it was not supposed to. it addresses the need for doubling
backslashes when a backslash character is an element of the regex.
foo = "foo\\n\n"
grep("\n", foo, perl=TRUE, value=TRUE)
mygrep("\n", foo, perl=TRUE, value=TRUE)
# both match the newline
grep("\\n", foo, perl=TRUE, value=TRUE)
mygrep("\\n", foo, perl=TRUE, value=TRUE)
# both match (guess what)
bar = "bar\n"
grep("\n", bar, perl=TRUE, value=TRUE)
mygrep("\n", bar, perl=TRUE, value=TRUE)
# both match the newline
grep("\\n", bar, perl=TRUE, value=TRUE)
mygrep("\\n", bar, perl=TRUE, value=TRUE)
# counterintuitively, grep matches (intuitively, it should match
backslash-n, not a newline, but there's just a newline in bar) -- i do
know why it matches, but i'm pretty sure for many of those who do it's
an inconvenient detail, and for those who don't it's a confusing annoyance
zee = "zee\\"
grep("\\", zee, perl=TRUE, value=TRUE)
mygrep("\\", zee, perl=TRUE, value=TRUE)
# grep fails, needs "\\\\"
conclusion? i'd opt for mygrep in my own code; i guessed this was what
john wanted, therefore the post.
vQ
here's another example of what could be considered r grep's idiosyncrasy:
grep("\\n", "\n", perl=TRUE)
# matches
grep("\\n", "\\n", perl=TRUE)
# matches
with everything else equal, "\\n" should match *either* newline *or*
backslash-n, no?
vQ