beam: add clamp primitive with tests

wizard-work/beam/clamp.py

@@ -0,0 +1,12 @@
+"""Clamp a value to [lo, hi]. Handles None by raising, preserves type."""
+from __future__ import annotations
+
+
+def clamp(value, lo, hi):
+    if lo > hi:
+        raise ValueError("lo > hi: %r > %r" % (lo, hi))
+    if value < lo:
+        return lo
+    if value > hi:
+        return hi
+    return value

wizard-work/beam/test_clamp.py

@@ -0,0 +1,20 @@
+import unittest
+from clamp import clamp
+
+
+class TestClamp(unittest.TestCase):
+    def test_basic(self):
+        self.assertEqual(clamp(5, 0, 10), 5)
+        self.assertEqual(clamp(-3, 0, 10), 0)
+        self.assertEqual(clamp(15, 0, 10), 10)
+    def test_bounds_equal(self):
+        self.assertEqual(clamp(5, 7, 7), 7)
+    def test_lo_gt_hi_raises(self):
+        with self.assertRaises(ValueError):
+            clamp(5, 10, 0)
+    def test_floats(self):
+        self.assertEqual(clamp(1.5, 0.0, 1.0), 1.0)
+
+
+if __name__ == "__main__":
+    unittest.main()