Oh, wait, I can get the behavior I want as a procedure, I just can't represent it as a single readtable on its own. I got stuck thinking that's what I had to do. Never mind! And thanks for kick-starting my brain, Matthew. :)
Carl Eastlund On Tue, May 31, 2011 at 11:06 PM, Carl Eastlund <[email protected]> wrote: > I don't believe so. I want to restore another readtable's behavior > for unmapped characters, but leave all other mappings in the current > readtable untouched. I can't think of a way to get my hand on > precisely that readtable. > > Specifically, I am trying to write a reader extension for dotted > accessors, so that x.y.z reads as (dot x y z) or something similar. > The way I envision implementing it is to first read a symbol using the > default symbol reader, leaving "." as a terminating character, then > checking for "." and chaining to a suffix if it is present. For this > to be a generic reader extension, that recursive read using the > underlying symbol reader should leave all other extensions in place. > I can only think of how to come up with the default readtable, or > perhaps the readtable as it was just prior to this extension, but all > subsequent extensions would be lost. > > Carl Eastlund > > On Tue, May 31, 2011 at 10:57 PM, Matthew Flatt <[email protected]> wrote: >> The `read/recursive' and `read-syntax/recursive' functions accept a >> readtable to use for the immediate read action, while nested reads use >> the `current-readtable' parameter. That's intended as a general >> chaining mechanism. Can you get the behavior you want by using those >> functions? >> >> At Tue, 31 May 2011 14:29:29 -0400, Carl Eastlund wrote: >>> The make-readtable function allows me to remap individual characters >>> to new behaviors, and to remap the default behavior of unmapped >>> characters to new behavior. It also allows me to remap individual >>> characters to the behavior of another readtable (such as the default >>> readtable). I cannot, however, remap the default behavior of unmapped >>> characters to the behavior of another readtable. (The same >>> restriction appears to hold for "dispatch macro" mappings.) Is there >>> a way to do this that I have missed? If not, could this ability be >>> added? >>> >>> Carl Eastlund _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
