Status: Passed, Mar 89 X3J13
Edit History: 21-Oct-88, Version 1 by Pitman
Version 2, KMP 3/30/89
Version 3, 9-Apr-89, Masinter
(Include discussion from Version 1)
There is no way to bind read syntax within a file.
As a result, applications which require extended syntax of some sort
tend to globally modify the lisp readtable at compile and load time,
sometimes interfering with other modules and/or user interaction.
Conscientious developers often avoid the creation of any stylized
syntax because of its likely effect on parts of the environment which
don't really belong to the application developer. This need for
paranoia is probably contrived and the result of what amounts to
an oversight in the design of Common Lisp.
Define that COMPILE-FILE and LOAD bind *READTABLE* to its current value.
This allows portable programs to do
(EVAL-WHEN (EVAL LOAD COMPILE)
(SETQ *READTABLE* FOO:MY-READTABLE))
at the top of a file without globally side-effecting the
Currently, there is no portable way to change the syntax only for
the duration of a file, which in turn makes customized syntax
difficult to use safely.
Programs that want to side effect the environment can instead
continue to modify *READTABLE*.
This is enough of a foothold to implement a more elaborate facility
for using readtables in a localized way.
Cost to Implementors:
Cost to Users:
Cost of Non-Adoption:
Readtables would continue to be hard to use in a clean way.
If people could use readtables safely, we might see more interesting
experimentation with read syntax.
A slight improvement to aesthetics by controlling what was formerly
an unbounded side-effect (modification to the global readtable).