Commit 6edecc9d authored by Tobias C. Rittweiler's avatar Tobias C. Rittweiler

Update docstrings.

parent 3a2117fe
This diff is collapsed.
......@@ -8,6 +8,7 @@
......@@ -20,6 +21,160 @@
;; Conditions
* What are Named-Readtables?
Named-Readtables is a library that provides a namespace for
readtables akin to the already-existing namespace of packages. In
* you can associate readtables with names, and retrieve
readtables from their names;
* you can associate source files with readtable names, and be
sure that the right readtable is active when compiling/loading
the file;
* similiarly, your development environment now has a chance to
automatically determine what readtable should be active while
processing source forms on interactive commands.
It follows that Named-Readtables is a facility for using readtables in
a localized way.
Additionally, it also attempts to become a facility for using
readtables in a /modular/ way. In particular:
* it provides a convenience macro to specify the whole content of
a readtable at one sight.
* it supports multiple inheritance.
* Notes on the API
The API heavily imitates the API of packages. This has the nice
property that any experienced Common Lisper will take it up totally
* Important API idiosyncrasies
There are three major differences between the API of Named-Readtables,
and the API of packages.
1. Readtable names are symbols not strings.
Time has shown that the fact that packages are named by
strings causes severe headache because of the potential of
package names colliding with each other.
Hence, readtables are named by symbols lest to make the
situation worse than it already is. Consequently, readtables
happily coexist next to each other. Or, taken to an extreme,
If, for example to duely signify the importance of your cool
readtable hack, you really think it deserves a global name,
you can always resort to keywords.
2. The inheritance is resolved statically, not dynamically.
A package that uses another package will have access to all
the other package's exported symbols, even to those that will
be added after its definition. I.e. the inheritance is
resolved at run-time, that is dynamically.
Unfortunately, we cannot do the same for readtables in a
portable manner.
Therefore, we do not talk about \"using\" another readtable
but about \"merging\" the other readtable's definition into
the readtable we are going to define. I.e. the inheritance is
resolved once at definition time, that is statically.
(Such merging can more or less be implemented portably albeit
at a certain cost. Most of the time, this cost manifests
itself at the time a readtable is defined, i.e. at
compile-time, and once for each definition, only, so it may
not bother you. Nonetheless, we provide extra support for
Sbcl, ClozureCL, and AllegroCL at the moment. Patches for your
implementation of choice are welcome, of course.)
3. DEFREADTABLE does not have compile-time effects.
If you define a package via DEFPACKAGE, you can make that
package the currently active package for the subsequent
compilation of the same file via IN-PACKAGE. The same is,
however, not true for DEFREADTABLE and IN-READTABLE for the
following reason:
It's unlikely that the need for special reader-macros arises
for a problem which can be solved in just one file. Most
often, you're going to define the reader macro functions, and
set up the corresponding readtable in an extra file.
If DEFREADTABLE had compile-time effects, you'd have to wrap
each definition of a reader-macro function in an EVAL-WHEN to
make its definition available at compile-time. Because that's
simply not the common case, DEFREADTABLE does not have a
compile-time effect.
If you want to use a readtable within the same file as its
definition, wrap the DEFREADTABLE and the reader-macro
function definitions in an explicit EVAL-WHEN.
* Preregistered Readtables
- NIL, and :STANDARD designate the /standard readtable/.
- :CURRENT designates the /current readtable/.
* Examples
> (defreadtable elisp:syntax
> (:merge :standard)
> (:macro-char #\\? #'elisp::read-character-literal t)
> (:macro-char #\\[ #'elisp::read-vector-literal t)
> ...
> (:case :preserve))
> (defreadtable scheme:syntax
> (:merge :standard)
> (:macro-char #\\[ #'(lambda (stream char)
> (read-delimited-list #\\] stream)))
> (:macro-char #\\# :dispatch)
> (:dispatch-macro-char #\\# #\\t #'scheme::read-#t)
> (:dispatch-macro-char #\\# #\\f #'scheme::read-#f)
> ...
> (:case :preserve))
> (in-readtable elisp:syntax)
> ...
> (in-readtable scheme:syntax)
(pushnew :named-readtables *features*)
\ No newline at end of file
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment