Implement *package* special var; package overhaul.

* eval.c (load): Rebind *package* in the local dynamic
environment already established for the sake of *load-path*.
By doing this we cause *package* to be restored to its
prior value, which allows the loaded file to alter it.
Common Lisp works this way.
(eval_init): Register *package* variable, with the
user package as its default value.

* lib.c (package_s): New symbol variable.
(intern, rehome_sym): Default the package argument to the
current package, not to user_package.
(get_user_package, get_system_package, get_keyword_package):
Functions removed.
(get_current_package): New function.
(obj_print_impl): Revise symbol printing. Keyword and
uninterned symbols are printed with : and #: prefixes.
The remainder are printed with a package prefix if their
home package isn't the current package.

* lib.h (keyword_package, user_package, system_package): These
macros are just straight aliases for the global
variables, not going through the lookup mechanism,
which was pointless.
(cur_package): New macro.
(package_s): Declared.
(get_current_package): Declared.

* lisplib.c (lisplib_try_load): Establish a local
dynamic environment, and bind the *package* variable
to the user package which the library modules expect.

* parser.c (find_matching_syms, provide_completions):
Treat unqualified symbols in the current package
rather than user package.

* parser.y (sym_helper): Intern unqualified symbols
in the current package, not user package.

* txr.1: Document that the variables user-package,
system-package and keyword-package should not be modified.
Document the *package* special variable, and that intern and
rehome-sym default their package argument to its value. (Here
we get rid of wrong references to the undocumented variable
*user-package*).

1 files changed, 21 insertions, 2 deletions

diff --git a/txr.1 b/txr.1
index 91127f58..68081588 100644
--- a/txr.1
+++ b/txr.1
@@ -38743,6 +38743,25 @@ a leading colon. The
 is for internal symbols, helping
 the implementation avoid name clashes with user code in some situations.
 
+These variables shouldn't be modified.  If they are modified, the consequences
+are unspecified.
+
+.coNP Special variable @ *package*
+.desc
+This variable holds the current package. The top-level binding of this
+variable is initialized to the user package: the same package object
+which is held in the
+.code user-package
+variable.
+
+The current package is used as the default package for interning symbol tokens
+which do not carry the colon-delimited package prefix.
+
+The current package also affects printing. When a symbol is printed whose
+home package matches the current package, it is printed without a package
+prefix. (Keyword symbols are always printed with the colon prefix, even if the
+keyword package is current.)
+
 .coNP Function @ make-sym
 .synb
 .mets (make-sym << name )
@@ -38901,7 +38920,7 @@ should be a package. If
 .meta package
 is not supplied, then the value
 taken is that of
-.codn *user-package* .
+.codn *package* .
 
 The
 .code intern
@@ -38930,7 +38949,7 @@ must be a symbol and package object,
 respectively. If
 .meta package
 is not given, then it defaults to the value of
-.codn *user-package* .
+.codn *package* .
 
 The
 .code rehome-sym