[Rd] grep with fixed=TRUE and ignore.case=TRUE

[Petr Savicky]

Dear R developers,

I suggest to modify the behaviour of "grep" function with fixed=TRUE option.

Currently, fixed=TRUE implies ignore.case=FALSE (overrides ignore.case=TRUE,
if set by the user).

I suggest to keep ignore.case as set by the user even if fixed=TRUE. Since
the default of ignore.case is FALSE, this would not change the behaviour
of grep, if the user does not set ignore.case explicitly.

In my opinion, fixed=TRUE is most useful for suppressing meta-character
expansion. On the other hand, for a simple word search, ignoring
case is sometimes useful.

If for some reason, it is better to keep the current behavior of grep, then I
suggest to extend the documentation as follows:

ORIGINAL:
   fixed: logical.  If 'TRUE', 'pattern' is a string to be matched as
          is.  Overrides all conflicting arguments.

SUGGESTED:
   fixed: logical.  If 'TRUE', 'pattern' is a string to be matched as
          is.  Overrides all conflicting arguments including ignore.case.

All the best, Petr Savicky.