a little pre-lunch decrufting and cleanup

1 files changed, 46 insertions, 0 deletions

diff --git a/lib/sqlalchemy/sql/operators.py b/lib/sqlalchemy/sql/operators.py
index 4ee5f4a18..19e0c484c 100644
--- a/lib/sqlalchemy/sql/operators.py
+++ b/lib/sqlalchemy/sql/operators.py
@@ -6,6 +6,8 @@
 from operator import and_, or_, inv, add, mul, sub, div, mod, truediv, \
      lt, le, ne, gt, ge, eq
 
+from sqlalchemy.util import Set
+
 def from_():
     raise NotImplementedError()
 
@@ -68,3 +70,47 @@ def desc_op(a):
 
 def asc_op(a):
     return a.asc()
+
+_commutative = Set([eq, ne, add, mul])
+def is_commutative(op):
+    return op in _commutative
+    
+_smallest = object()
+_largest = object()
+
+_PRECEDENCE = {
+    from_:15,
+    mul:7,
+    div:7,
+    mod:7,
+    add:6,
+    sub:6,
+    concat_op:6,
+    ilike_op:5,
+    notilike_op:5,
+    like_op:5,
+    notlike_op:5,
+    in_op:5,
+    notin_op:5,
+    is_:5,
+    isnot:5,
+    eq:5,
+    ne:5,
+    gt:5,
+    lt:5,
+    ge:5,
+    le:5,
+    between_op:5,
+    distinct_op:5,
+    inv:5,
+    and_:3,
+    or_:2,
+    comma_op:-1,
+    as_:-1,
+    exists:0,
+    _smallest: -1000,
+    _largest: 1000
+}
+
+def is_precedent(operator, against):
+    return _PRECEDENCE.get(operator, _PRECEDENCE[_smallest]) <= _PRECEDENCE.get(against, _PRECEDENCE[_largest])