Ben Bolker bbol...@gmail.com
on Thu, 15 Sep 2011 11:03:26 +0200 writes:
Inspired by
http://stackoverflow.com/questions/7487778/could-you-tell-me-what-this-error-means
I wrote the following very small (one-line) patch which
returns an *informative* error message when R tries to
load a zero-byte file rather than
Error in if (!grepl(RD[AX]2\n, magic)) { : argument is
of length zero
I would guess that error messages with the word magic
in them would be disturbing to new users, who are probably
worried already that R is magic ...
:-) indeed...
While it would not be a good idea to program around such error
messages in general, as each extra if(...) is executed everytime
the function is called, i.e. has a (albeit *very small*) penalty for
every correct call just for the sake of that message in the
erronous call case,
I do agree that it is worth here and so have added it (for
R-devel only).
Thank you, Ben.
Ben Bolker
--
Index: load.R
===
--- load.R(revision 56743)
+++ load.R(working copy)
@@ -25,6 +25,7 @@
## Since the connection is not open this opens it in binary mode
## and closes it again.
magic - readChar(con, 5L, useBytes = TRUE)
+if (length(magic)==0) stop(empty (zero-byte) file)
if (!grepl(RD[AX]2\n, magic)) {
## a check while we still know the call to load()
if(grepl(RD[ABX][12]\r, magic))
--
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