Move -IV (operator) correctly to lhs

cpmpy/transformations/linearize.py

@@ -264,35 +264,29 @@ def canonical_comparison(lst_of_expr):
         if isinstance(cpm_expr, Comparison):
             lhs, rhs = cpm_expr.args
 
-            # bring all vars to lhs
             if is_num(lhs) or isinstance(lhs, _NumVarImpl) or (isinstance(lhs, Operator) and lhs.name in {"sum", "wsum"}):
+                # bring all vars to lhs
+                lhs2 = []
                 if isinstance(rhs, _NumVarImpl):
-                    if isinstance(lhs, Operator) and lhs.name == "sum":
-                        lhs, rhs = sum([1 * a for a in lhs.args] + [-1 * rhs]), 0
-                    elif isinstance(lhs, _NumVarImpl) or (isinstance(lhs, Operator) and lhs.name == "wsum"):
-                        lhs, rhs = lhs + -1 * rhs, 0
-                    else:
-                        raise ValueError(
-                            f"unexpected expression on lhs of expression, should be sum,wsum or intvar but got {lhs}")
+                    lhs2, rhs = [-1 * rhs], 0
                 elif isinstance(rhs, Operator) and rhs.name == "sum":
-                    if isinstance(lhs, Operator) and lhs.name == "sum":
-                        lhs, rhs = sum([1 * a for a in lhs.args] + [-1 * b for b in rhs.args
-                                    if (isinstance(b, _NumVarImpl) or isinstance(b, Operator))]), sum(b for b in rhs.args if is_num(b))
-                    elif isinstance(lhs, _NumVarImpl) or (isinstance(lhs, Operator) and lhs.name == "wsum"):
-                        lhs, rhs = lhs + [-1 * b for b in rhs.args
-                                    if (isinstance(b, _NumVarImpl) or isinstance(b, Operator))], sum(b for b in rhs.args if is_num(b))
+                    lhs2, rhs = [-1 * b if isinstance(b, _NumVarImpl) else 1 * b for b in rhs.args
+                                 if isinstance(b, _NumVarImpl) or isinstance(b, Operator)], \
+                                 sum(b for b in rhs.args if is_num(b))
                 elif isinstance(rhs, Operator) and rhs.name == "wsum":
-                    if isinstance(lhs, Operator) and lhs.name == "sum":
-                        lhs, rhs = sum([1 * a for a in lhs.args] + [-a * b for a, b in zip(rhs.args[0], rhs.args[1])
-                                    if isinstance(b, _NumVarImpl)]), \
-                                   sum(-a * b for a, b in zip(rhs.args[0], rhs.args[1])
-                                     if not isinstance(b, _NumVarImpl))
-                    elif isinstance(lhs, _NumVarImpl) or (isinstance(lhs, Operator) and lhs.name == "wsum"):
-                        lhs, rhs = lhs + sum([-a * b for a, b in zip(rhs.args[0], rhs.args[1])
-                                    if isinstance(b, _NumVarImpl)]), \
-                                   sum(-a * b for a, b in zip(rhs.args[0], rhs.args[1])
+                    lhs2, rhs = [-a * b for a, b in zip(rhs.args[0], rhs.args[1])
+                                    if isinstance(b, _NumVarImpl)], \
+                                    sum(-a * b for a, b in zip(rhs.args[0], rhs.args[1])
                                     if not isinstance(b, _NumVarImpl))
 
+                if isinstance(lhs, Operator) and lhs.name == "sum":
+                    lhs, rhs = sum([1 * a for a in lhs.args] + lhs2), rhs
+                elif isinstance(lhs, _NumVarImpl) or (isinstance(lhs, Operator) and lhs.name == "wsum"):
+                    lhs, rhs = lhs + lhs2, rhs
+                else:
+                    raise ValueError(
+                        f"unexpected expression on lhs of expression, should be sum,wsum or intvar but got {lhs}")
+
                 assert not is_num(lhs), "lhs cannot be an integer at this point!"
 
                 # bring all const to rhs