fixing register of loaded packages in

Author: mmatera

mathics/builtin/files.py

@@ -3692,7 +3692,7 @@ def apply_name(self, name, evaluation):
 
 
 class Compress(Builtin):
-    """
+    u"""
     <dl>
     <dt>'Compress[$expr$]'
       <dd>gives a compressed string representation of $expr$.
@@ -4800,7 +4800,6 @@ def apply(self, pathname, evaluation):
             return SymbolTrue
         return SymbolFalse
 
-
 class Needs(Builtin):
     """
     <dl>
@@ -4912,18 +4911,34 @@ class Needs(Builtin):
     }
 
     def apply(self, context, evaluation):
-        "Needs[context_String]"
-
-        if not valid_context_name(context.get_string_value()):
-            evaluation.message("Needs", "ctx", Expression("Needs", context), 1, "`")
+        'Needs[context_String]'
+        contextstr = context.get_string_value()
+        if contextstr == "":
+            return Symbol("Null")
+        if contextstr[0]=="`":
+            curr_ctxt = evaluation.definitions.get_current_context()
+            contextstr = curr_ctxt + contextstr[1:]
+            context = String(contextstr)
+
+        if not valid_context_name(contextstr):
+            evaluation.message('Needs', 'ctx', Expression(
+                'Needs', context), 1, '`')
             return
         test_loaded = Expression("MemberQ", Symbol("$Packages"), context)
         test_loaded = test_loaded.evaluate(evaluation)
         if test_loaded.is_true():
             # Already loaded
             return SymbolNull
 
-        result = Expression("Get", context).evaluate(evaluation)
+        # TODO: Look why this rises the message
+        # "Select::normal: Nonatomic expression expected."
+        already_loaded = Expression('MemberQ',
+                                    Symbol('System`$Packages'), context)
+        already_loaded = already_loaded.evaluate(evaluation).is_true()
+        if already_loaded:
+           return Symbol('Null')
+
+        result = Expression('Get', context).evaluate(evaluation)
 
         if result == Symbol("$Failed"):
             evaluation.message("Needs", "nocont", context)

mathics/builtin/system.py

@@ -230,18 +230,18 @@ class Packages(Predefined):
     </dl>
 
     X> $Packages
-    = {CombinatoricaOld,ImportExport,Internal,System,XML}
-    #> MemberQ[$Packages, "System"]
+    = {CombinatoricaOld`,ImportExport`,Internal`,System`,XML`}
+    #> MemberQ[$Packages, "System`"]
     = True
     """
 
     name = "$Packages"
-
-    def evaluate(self, evaluation):
-        return Expression(
-            "List",
-            *(String(name) for name in evaluation.definitions.get_package_names()),
-        )
+    rules = {'$Packages': '{"CombinatoricaOld`","ImportExport`","Internal`","System`","XML`"}',}
+    # def evaluate(self, evaluation):
+    #    return Expression(
+    #        "List",
+    #        *(String(name) for name in evaluation.definitions.get_package_names()),
+    #    )
 
 
 class ParentProcessID(Predefined):

mathics/core/definitions.py

@@ -389,7 +389,10 @@ def lookup_name(self, name) -> str:
         return with_context
 
     def get_package_names(self) -> typing.List[str]:
-        return sorted({name.split("`")[0] for name in self.get_names()})
+        # TODO: load from $Packages...
+        pass
+    
+        #return sorted({name.split("`")[0] for name in self.get_names()})
 
     def shorten_name(self, name_with_ctx) -> str:
         if "`" not in name_with_ctx: