pattern in history

Hi,

Sometimes I need to consult the history of commands that are matching a
regex, so I modified the utils::history function for that purpose. I
found it useful.

I append the code ( I only added the two lines with #**)

Romain.


history2 <-
function (pattern="", max.show = 25, reverse = FALSE, unique =
pattern!="", ...)
{
   file1 <- tempfile("Rrawhist")
   savehistory(file1)
   rawhist <- scan(file1, what = "", quiet = TRUE, sep = "\n")
   rawhist <- rawhist[grep(pattern, rawhist, ...)] #**
   if(unique) rawhist <- unique(rawhist) #**
   unlink(file1)
   nlines <- length(rawhist)

   inds <- max(1, nlines - max.show):nlines
   if (reverse)
       inds <- rev(inds)
   file2 <- tempfile("hist")
   write(rawhist[inds], file2)
   file.show(file2, title = "R History", delete.file = TRUE)
}

That's an interesting suggestion, but

1) it is not a good idea to change the order of arguments in a function.

2) is the 'unique' argument useful?  I cannot see it being used if
there is no pattern search, nor I do see the merit in showing repeated 
lines if I have subselected.

3) like ls(), testing if 'pattern' were missing or NULL would be a 
better idea.

Le 11.04.2006 14:12, Prof Brian Ripley a ?crit :

That's an interesting suggestion, but

1) it is not a good idea to change the order of arguments in a function.

Yes, my mystake. It's because i like to call 'history(something)' directly 
and not 'history(pattern=something)'.
I hadn't in mind the possibility to break existing code.

2) is the 'unique' argument useful?  I cannot see it being used if
there is no pattern search, nor I do see the merit in showing repeated 
lines if I have subselected.

3) like ls(), testing if 'pattern' were missing or NULL would be a better 
idea.

Right.
There is also a problem with the order of the calls.
If I do :

ls()
l <- mean(rnorm(50))
ls()
history(pattern="^l")

it prints :
ls()
l <- mean(rnorm(50))

when it should print :
l <- mean(rnorm(50))
ls()

We can use rev twice (like in history3 below), but is it worth it ?

history3 <-
function (max.show = 25, reverse = FALSE, pattern, ...)
{
 file1 <- tempfile("Rrawhist")
 savehistory(file1)
 rawhist <- scan(file1, what = "", quiet = TRUE, sep = "\n")
 if(!missing(pattern)) rawhist <- rev( unique( rev(rawhist[grep(pattern, 
rawhist, ...)] ) ) )
 unlink(file1)
 nlines <- length(rawhist)
   inds <- max(1, nlines - max.show):nlines
 if (reverse)
     inds <- rev(inds)
 file2 <- tempfile("hist")
 write(rawhist[inds], file2)
 file.show(file2, title = "R History", delete.file = TRUE)
}