# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1484515054 -3600
# Node ID 5969ebcb3cc11e5dd6c2f7c157238b2785962a1e
# Parent  dde129595d21816bcfb3b00a7f0d08e6e78ec527
Added clear and __delitem__ methods to the dictionary implementation.

diff -r dde129595d21 -r 5969ebcb3cc1 lib/__builtins__/dict.py
--- a/lib/__builtins__/dict.py	Sun Jan 15 18:59:16 2017 +0100
+++ b/lib/__builtins__/dict.py	Sun Jan 15 22:17:34 2017 +0100
@@ -33,8 +33,7 @@
 
         "Initialise the dictionary."
 
-        self.size = 0
-        self.buckets = self._get_buckets(args is not None and len(args) / 2 or 0)
+        self.clear()
 
         if args is not None:
             for key, value in args:
@@ -80,6 +79,20 @@
 
         return buckets
 
+    def _get_entry(self, key):
+
+        "Return the index and entry index as a tuple for 'key'."
+
+        # Find an index identifying the bucket involved.
+
+        index = self._get_index(key)
+
+        # Find the entry index within the bucket of the key.
+
+        i = self._find_entry(key, index)
+
+        return index, i
+
     def _get_index(self, key):
 
         "Check 'key' and return an index or raise TypeError."
@@ -119,13 +132,7 @@
 
         "Set in the 'buckets' an item having the given 'key' and 'value'."
 
-        # Find an index identifying the bucket involved.
-
-        index = self._get_index(key)
-
-        # Find the entry index within the bucket of the key.
-
-        i = self._find_entry(key, index)
+        index, i = self._get_entry(key)
 
         # With no existing entry, append to the bucket.
 
@@ -138,6 +145,32 @@
         else:
             buckets[index][i] = key, value
 
+    # Public special methods.
+
+    def __delitem__(self, key):
+
+        "Remove the entry associated with the given 'key' from this dictionary."
+
+        index, i = self._get_entry(key)
+
+        if index is None or i is None:
+            raise KeyError, key
+
+        del self.buckets[index][i]
+        self.size -= 1
+
+    def __getitem__(self, key):
+
+        "Return the value associated with 'key' from the dictionary."
+
+        return self.get(key, self.MISSING)
+
+    def __iter__(self):
+
+        "Return an iterator."
+
+        return itemiterator(self.keys())
+
     def __setitem__(self, key, value):
 
         "Set a mapping from 'key' to 'value' in the dictionary."
@@ -149,13 +182,14 @@
 
         self._setitem(self.buckets, key, value)
 
-    def __delitem__(self, key, value): pass
+    # Public conventional methods.
 
-    def __getitem__(self, key):
+    def clear(self):
 
-        "Return the value associated with 'key' from the dictionary."
+        "Reset the dictionary to an empty state."
 
-        return self.get(key, self.MISSING)
+        self.size = 0
+        self.buckets = self._get_buckets(0)
 
     def get(self, key, default=None):
 
@@ -164,13 +198,7 @@
         the dictionary, 'default' will be returned instead.
         """
 
-        # Find an index identifying the bucket involved.
-
-        index = self._get_index(key)
-
-        # Find the entry index within the bucket of the key.
-
-        i = self._find_entry(key, index)
+        index, i = self._get_entry(key)
 
         # With no entry index, either raise an exception or return the default.
 
@@ -185,9 +213,11 @@
         else:
             return self.buckets[index][i][1]
 
-    def clear(self): pass
+    def has_key(self, key):
 
-    def has_key(self): pass
+        "Return whether the given 'key' is used with this dictionary."
+
+        return self.get(key) and True or False
 
     def keys(self):
 
@@ -198,15 +228,6 @@
             l.append(key)
         return l
 
-    def values(self):
-
-        "Return the values in this dictionary."
-
-        l = []
-        for key, value in self.items():
-            l.append(value)
-        return l
-
     def items(self):
 
         "Return the items, each being a (key, value) tuple, in this dictionary."
@@ -217,12 +238,16 @@
         return l
 
     def setdefault(self, key, value): pass
+
     def update(self, other): pass
 
-    def __iter__(self):
+    def values(self):
+
+        "Return the values in this dictionary."
 
-        "Return an iterator."
-
-        return itemiterator(self.keys())
+        l = []
+        for key, value in self.items():
+            l.append(value)
+        return l
 
 # vim: tabstop=4 expandtab shiftwidth=4
diff -r dde129595d21 -r 5969ebcb3cc1 tests/dict.py
--- a/tests/dict.py	Sun Jan 15 18:59:16 2017 +0100
+++ b/tests/dict.py	Sun Jan 15 22:17:34 2017 +0100
@@ -18,6 +18,8 @@
     print "d[30]: key not found", exc.key
 print d.get(30)                         # None
 print d.get(30, "c")                    # c
+print d.has_key(20)                     # True
+print d.has_key(30)                     # False
 
 l = f(d)
 print "# l: ",
@@ -60,3 +62,17 @@
     print d[[1, 2]]
 except TypeError:
     print "d[[1, 2]]: key not appropriate"
+
+# Attempt to remove items.
+
+del d[20]
+print d.has_key(20)                     # False
+try:
+    del d[30]                           # should fail with an exception
+except KeyError, exc:
+    print "del d[30]: key not found", exc.key
+
+# Clear the dictionary.
+
+d.clear()
+print d                                 # {}