# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1481323907 -3600
# Node ID 209dc7a270fd15b8c27e2e99f2bab706122f387e
# Parent  65ff81f922d309b5995114e5951a4c37312f5714
Added support for dynamic attribute access using getattr and hasattr, employing
a special attribute on strings to hold the object table code and position for
any attribute having the same name as the represented string.

diff -r 65ff81f922d3 -r 209dc7a270fd generator.py
--- a/generator.py	Fri Dec 09 23:30:41 2016 +0100
+++ b/generator.py	Fri Dec 09 23:51:47 2016 +0100
@@ -56,6 +56,7 @@
     # NOTE: These must be synchronised with the library.
 
     function_type = "__builtins__.core.function"
+    string_type = "__builtins__.str.string"
     type_type = "__builtins__.core.type"
 
     predefined_constant_members = (
@@ -491,6 +492,14 @@
         if data is not None:
             attrs["__data__"] = data
 
+            # Also set a key for dynamic attribute lookup, if a string.
+
+            if cls == self.string_type:
+                if data in self.optimiser.all_attrnames:
+                    attrs["__key__"] = data
+                else:
+                    attrs["__key__"] = None
+
         # Define the structure details. An object is created for the constant,
         # but an attribute is provided, referring to the object, for access to
         # the constant in the program.
@@ -871,6 +880,13 @@
                                                       encode_literal_constant_value(attr)))
                     continue
 
+                # Special internal key member.
+
+                elif attrname == "__key__":
+                    structure.append("{.code=%s, .pos=%s}" % (attr and encode_symbol("code", attr) or "0",
+                                                              attr and encode_symbol("pos", attr) or "0"))
+                    continue
+
                 # Special cases.
 
                 elif attrname in ("__file__", "__fname__",  "__mname__", "__name__"):
diff -r 65ff81f922d3 -r 209dc7a270fd lib/__builtins__/attribute.py
--- a/lib/__builtins__/attribute.py	Fri Dec 09 23:30:41 2016 +0100
+++ b/lib/__builtins__/attribute.py	Fri Dec 09 23:51:47 2016 +0100
@@ -19,19 +19,11 @@
 this program.  If not, see <http://www.gnu.org/licenses/>.
 """
 
+from __builtins__.types import check_string
 from native import object_getattr
 
 _default=object() # a unique placeholder for a missing value
 
-def _getattr(obj, name, default=_default):
-
-    """
-    Return for 'obj' the attribute having the given 'name', returning the given
-    'default' if the attribute is not defined for 'obj'.
-    """
-
-    return object_getattr(obj, name, default)
-
 def getattr(obj, name, default=_default):
 
     """
@@ -40,13 +32,27 @@
     'default' is not indicated and the attribute is not defined.
     """
 
-    result = _getattr(obj, name, default)
+    check_string(name)
+
+    # Attempt to obtain the attribute. If the name is not recognised as an
+    # attribute name, the default will be returned. Otherwise, an access
+    # operation will be attempted.
+
+    try:
+        result = object_getattr(obj, name, default)
+
+    # Handle exceptions when the access operation fails.
+
+    except TypeError:
+        result = _default
+
+    # Check the result and, if it is the placeholder value, raise an exception.
 
     if result is _default:
-        if default is _default:
-            raise AttributeError(name)
-        else:
-            return default
+        raise AttributeError(name)
+
+    # Otherwise, return the obtained value or supplied default.
+
     else:
         return result
 
@@ -54,8 +60,15 @@
 
     "Return whether 'obj' has an attribute called 'name'."
 
-    result = _getattr(obj, name)
-    return result is not _default
+    try:
+        getattr(obj, name)
+    except AttributeError:
+        return False
+    else:
+        return True
+
+# NOTE: setattr would probably only be supported on instances due to deductions
+# NOTE: applying to static objects being undermined by dynamic modifications.
 
 def setattr(obj, name, value): pass
 
diff -r 65ff81f922d3 -r 209dc7a270fd lib/__builtins__/str.py
--- a/lib/__builtins__/str.py	Fri Dec 09 23:30:41 2016 +0100
+++ b/lib/__builtins__/str.py	Fri Dec 09 23:51:47 2016 +0100
@@ -42,6 +42,12 @@
 
         self.__data__ = None
 
+        # Note the __key__ member. This is also initialised statically. Where
+        # a string is the same as an attribute name, the __key__ member contains
+        # attribute position and code details.
+
+        self.__key__ = None
+
     def __hash__(self):
 
         "Return a value for hashing purposes."
diff -r 65ff81f922d3 -r 209dc7a270fd templates/native/common.c
--- a/templates/native/common.c	Fri Dec 09 23:30:41 2016 +0100
+++ b/templates/native/common.c	Fri Dec 09 23:51:47 2016 +0100
@@ -36,9 +36,10 @@
 
 __attr __new_str(char *s)
 {
-    /* Create a new string and mutate the __data__ attribute. */
+    /* Create a new string and mutate the __data__ and __key__ attributes. */
     __attr attr = __new(&__InstanceTable___builtins___str_string, &__builtins___str_string, sizeof(__obj___builtins___str_string));
     attr.value->attrs[__pos___data__].strvalue = s;
+    attr.value->attrs[__pos___key__] = (__attr) {0, 0};
     return attr;
 }
 
diff -r 65ff81f922d3 -r 209dc7a270fd templates/native/introspection.c
--- a/templates/native/introspection.c	Fri Dec 09 23:30:41 2016 +0100
+++ b/templates/native/introspection.c	Fri Dec 09 23:51:47 2016 +0100
@@ -31,9 +31,13 @@
     __attr * const obj = &__args[1];
     __attr * const name = &__args[2];
     __attr * const _default = &__args[3];
+    /* name.__data__ interpreted as string */
+    __attr key = __load_via_object(name->value, __pos___key__);
 
-    /* NOTE: To be written. */
-    return __builtins___none_None;
+    if ((key.code == 0) && (key.pos == 0))
+        return *_default;
+    else
+        return __check_and_load_via_any(obj->value, key.pos, key.code);
 }
 
 static int __issubclass(__ref obj, __attr cls)
diff -r 65ff81f922d3 -r 209dc7a270fd templates/types.h
--- a/templates/types.h	Fri Dec 09 23:30:41 2016 +0100
+++ b/templates/types.h	Fri Dec 09 23:51:47 2016 +0100
@@ -57,6 +57,7 @@
         __obj * context;        /* attribute context */
         unsigned int min;       /* minimum number of parameters */
         __obj * b;              /* bound callable object */
+        unsigned int code;      /* parameter table code for key */
     };
 
     /* One of... */
@@ -64,6 +65,7 @@
     {
         __obj * value;          /* attribute value */
         const __ptable * ptable;/* parameter table */
+        unsigned int pos;       /* parameter table position for key */
         struct __attr (*fn)();  /* callable details */
 
         int intvalue;           /* integer value */
diff -r 65ff81f922d3 -r 209dc7a270fd tests/getattr.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/getattr.py	Fri Dec 09 23:51:47 2016 +0100
@@ -0,0 +1,38 @@
+class C:
+    def __init__(self):
+        self.x = 1
+        self.y = 2
+        self.z = 3
+
+class D:
+    def __init__(self):
+        self.x = 4
+        self.y = 5
+        self.z = 6
+
+c = C()
+d = D()
+
+attrnames = ["a", "b", "c", "x", "y", "z"]
+
+print ". c d"
+
+for attrname in attrnames:
+    print attrname, hasattr(c, attrname) and "1" or "0", hasattr(d, attrname) and "1" or "0"
+
+print
+print ". c d"
+
+for attrname in attrnames:
+    print attrname,
+    try:
+        v = getattr(c, attrname)
+        print "", v,
+    except AttributeError:
+        print " ?",
+
+    try:
+        v = getattr(d, attrname)
+        print "", v
+    except AttributeError:
+        print " ?"