A possible regex bug when working with large strings. The
following code snippet
t5 <- paste( c( "# === TEST", rep(' ', 2452294) ), collapse='')
str( sub("^.*TEST", "xyz", t5) )
str( sub("^.*TEST", "xyz", substr(t5,0,200)) )
doesn't behave right; on one machine, the second and third
lines print different results [the second line, on the long
string, doesn't do the substitution], while on another, the
second line causes a segfault. Both are running R 1.8.1
with PCRE, under NetBSD (1.6.1 and 1.6 respectively).
Possible related (although perhaps not a bug):
function(n) {
line <- paste(as.character(trunc(runif(n)*100)),collapse=" ")
system.time( rep <- gsub("[[:space:]]", "-", line) )
}
gives rather long times rising v sharply for big strings (eg
2.2s at n=2e4, 360s at n=2e5 on AMD 1.2GHz). Other languages
aren't so slow on this task (eg n=2e5: 0.4s ruby 1.8.1, and
5.2s python 2). Doubtless my extremely-quick-hack benchmarks
aren't fair, but the difference still seems rather big.
Mark <><
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