1 files changed, 30 insertions, 0 deletions
diff --git a/lib/spack/external/functools.py b/lib/spack/external/functools.py
new file mode 100644
index 0000000000..19f0903c82
--- /dev/null
+++ b/lib/spack/external/functools.py
@@ -0,0 +1,30 @@
+#
+# Backport of Python 2.7's total_ordering.
+#
+
+def total_ordering(cls):
+    """Class decorator that fills in missing ordering methods"""
+    convert = {
+        '__lt__': [('__gt__', lambda self, other: not (self < other or self == other)),
+                   ('__le__', lambda self, other: self < other or self == other),
+                   ('__ge__', lambda self, other: not self < other)],
+        '__le__': [('__ge__', lambda self, other: not self <= other or self == other),
+                   ('__lt__', lambda self, other: self <= other and not self == other),
+                   ('__gt__', lambda self, other: not self <= other)],
+        '__gt__': [('__lt__', lambda self, other: not (self > other or self == other)),
+                   ('__ge__', lambda self, other: self > other or self == other),
+                   ('__le__', lambda self, other: not self > other)],
+        '__ge__': [('__le__', lambda self, other: (not self >= other) or self == other),
+                   ('__gt__', lambda self, other: self >= other and not self == other),
+                   ('__lt__', lambda self, other: not self >= other)]
+    }
+    roots = set(dir(cls)) & set(convert)
+    if not roots:
+        raise ValueError('must define at least one ordering operation: < > <= >=')
+    root = max(roots)       # prefer __lt__ to __le__ to __gt__ to __ge__
+    for opname, opfunc in convert[root]:
+        if opname not in roots:
+            opfunc.__name__ = opname
+            opfunc.__doc__ = getattr(int, opname).__doc__
+            setattr(cls, opname, opfunc)
+    return cls