Support operator bool() for C++ classes.

CHANGES.rst

@@ -68,6 +68,8 @@ Features added
 * External C++ classes that overload the assignment operator can be used.
   Patch by Ian Henriksen.
 
+* Support operator bool() for C++ classes so they can be used in if statements.
+
 Bugs fixed
 ----------
 

Cython/Compiler/ExprNodes.py

@@ -846,6 +846,12 @@ class ExprNode(Node):
             return self
         elif type.is_pyobject or type.is_int or type.is_ptr or type.is_float:
             return CoerceToBooleanNode(self, env)
+        elif type.is_cpp_class:
+            return SimpleCallNode(
+                self.pos,
+                function=AttributeNode(
+                    self.pos, obj=self, attribute='operator bool'),
+                args=[]).analyse_types(env)
         elif type.is_ctuple:
             bool_value = len(type.components) == 0
             return BoolNode(self.pos, value=bool_value,

Cython/Compiler/Parsing.py

@@ -2543,7 +2543,8 @@ supported_overloaded_operators = cython.declare(set, set([
     '+', '-', '*', '/', '%',
     '++', '--', '~', '|', '&', '^', '<<', '>>', ',',
     '==', '!=', '>=', '>', '<=', '<',
-    '[]', '()', '!', '='
+    '[]', '()', '!', '=',
+    'bool',
 ]))
 
 def p_c_simple_declarator(s, ctx, empty, is_type, cmethod_flag,
@@ -2620,6 +2621,13 @@ def p_c_simple_declarator(s, ctx, empty, is_type, cmethod_flag,
                     s.error("Overloading operator '%s' not yet supported." % op,
                             fatal=False)
                 name += op
+            elif op == 'IDENT':
+                op = s.systring;
+                if op not in supported_overloaded_operators:
+                    s.error("Overloading operator '%s' not yet supported." % op,
+                            fatal=False)
+                name = name + ' ' + op
+                s.next()
         result = Nodes.CNameDeclaratorNode(pos,
             name = name, cname = cname, default = rhs)
     result.calling_convention = calling_convention

tests/run/cpp_operators.pyx

@@ -7,6 +7,7 @@ cimport cython.operator
 from cython.operator cimport dereference as deref
 
 from libc.string cimport const_char
+from libcpp cimport bool
 
 cdef out(s, result_type=None):
     print '%s [%s]' % (s.decode('ascii'), result_type)
@@ -49,6 +50,12 @@ cdef extern from "cpp_operators_helper.h":
         const_char* operator[](int)
         const_char* operator()(int)
 
+    cppclass TruthClass:
+        TruthClass()
+        TruthClass(bool)
+        bool operator bool()
+        bool value
+
 def test_unops():
     """
     >>> test_unops()
@@ -148,3 +155,30 @@ def test_index_call():
     out(t[0][100], typeof(t[0][100]))
     out(t[0](100), typeof(t[0](100)))
     del t
+
+def test_bool_op():
+    """
+    >>> test_bool_op()
+    """
+    cdef TruthClass yes = TruthClass(True)
+    cdef TruthClass no = TruthClass(False)
+    if yes:
+        pass
+    else:
+        assert False
+    if no:
+        assert False
+
+def test_bool_cond():
+    """
+    >>> test_bool_cond()
+    """
+    assert (TruthClass(False) or TruthClass(False)).value == False
+    assert (TruthClass(False) or TruthClass(True)).value == True
+    assert (TruthClass(True) or TruthClass(False)).value == True
+    assert (TruthClass(True) or TruthClass(True)).value == True
+
+    assert (TruthClass(False) and TruthClass(False)).value == False
+    assert (TruthClass(False) and TruthClass(True)).value == False
+    assert (TruthClass(True) and TruthClass(False)).value == False
+    assert (TruthClass(True) and TruthClass(True)).value == True

tests/run/cpp_operators_helper.h

@@ -45,3 +45,11 @@ public:
     BIN_OP(());
 
 };
+
+class TruthClass {
+public:
+  TruthClass() : value(false) {}
+  TruthClass(bool value) : value(value) {}
+  operator bool() { return value; }
+  bool value;
+};