Wrap literal constants in parenthesis in c-impl of ScalarOps

pytensor/scalar/basic.py

@@ -4349,7 +4349,7 @@ class Composite(ScalarInnerGraphOp):
                 if var not in self.fgraph.inputs:
                     # This is an orphan
                     if isinstance(var, Constant) and isinstance(var.type, CLinkerType):
-                        subd[var] = var.type.c_literal(var.data)
+                        subd[var] = f"({var.type.c_literal(var.data)})"
                     else:
                         raise ValueError(
                             "All orphans in the fgraph to Composite must"
@@ -4408,7 +4408,7 @@ class Composite(ScalarInnerGraphOp):
         return self.c_code_template % d
 
     def c_code_cache_version_outer(self) -> tuple[int, ...]:
-        return (4,)
+        return (5,)
 
 
 class Compositef32:

pytensor/scalar/loop.py

@@ -239,7 +239,7 @@ class ScalarLoop(ScalarInnerGraphOp):
                 if var not in self.fgraph.inputs:
                     # This is an orphan
                     if isinstance(var, Constant) and isinstance(var.type, CLinkerType):
-                        subd[var] = var.type.c_literal(var.data)
+                        subd[var] = f"({var.type.c_literal(var.data)})"
                     else:
                         raise ValueError(
                             "All orphans in the fgraph to ScalarLoop must"
@@ -342,4 +342,4 @@ class ScalarLoop(ScalarInnerGraphOp):
         return res
 
     def c_code_cache_version_outer(self):
-        return (2,)
+        return (3,)

tests/scalar/test_basic.py

@@ -36,6 +36,7 @@ from pytensor.scalar.basic import (
     floats,
     int8,
     int32,
+    int64,
     ints,
     invert,
     log,
@@ -44,6 +45,7 @@ from pytensor.scalar.basic import (
     log10,
     mean,
     mul,
+    neg,
     neq,
     rad2deg,
     reciprocal,
@@ -156,6 +158,21 @@ class TestComposite:
             (literal_value + test_y) * (test_x / test_y),
         )
 
+    def test_negative_constant(self):
+        # Test that a negative constant is wrapped in parentheses to avoid confusing - (unary minus) and -- (decrement)
+        x = int64("x")
+        e = neg(constant(-1.5)) % x
+        comp_op = Composite([x], [e])
+        comp_node = comp_op.make_node(x)
+
+        c_code = comp_node.op.c_code(comp_node, "dummy", ["x", "y"], ["z"], dict(id=0))
+        assert "-1.5" in c_code
+
+        g = FunctionGraph([x], [comp_node.out])
+        fn = make_function(DualLinker().accept(g))
+        assert fn(2) == 1.5
+        assert fn(1) == 0.5
+
     def test_many_outputs(self):
         x, y, z = floats("xyz")
         e0 = x + y + z