beam: fix unary-vs-power precedence in expr_eval (-2**2 now -(2**2))

wizard-work/beam/expr_eval.py

@@ -111,7 +111,8 @@ class Parser:
     def parse_unary(self):
         if self.peek()[0] == 'op' and self.peek()[1] in ('+', '-'):
             op = self.advance()[1]
-            v = self.parse_unary()
+            # operand is a full power expression so that -2**2 == -(2**2)
+            v = self.parse_factor()
             return -v if op == '-' else v
         return self.parse_primary()
 

wizard-work/beam/test_expr_eval.py

@@ -0,0 +1,56 @@
+import math
+import sys, os
+sys.path.insert(0, os.path.dirname(__file__))
+from expr_eval import evaluate, EvalError
+
+def test_basic():
+    assert evaluate("2 + 3 * 4") == 14
+    assert evaluate("(2+3)*4") == 20
+    assert evaluate("10 / 3") == 10/3
+    assert evaluate("10 // 3") == 3
+    assert evaluate("10 % 3") == 1
+
+def test_power_precedence():
+    # unary binds looser than ** (matches Python)
+    assert evaluate("-2**2") == -4
+    assert evaluate("(-2)**2") == 4
+    assert evaluate("2**-2") == 0.25
+    assert evaluate("2**3**2") == 512
+
+def test_unary():
+    assert evaluate("--5") == 5
+    assert evaluate("-(-3)") == 3
+
+def test_funcs():
+    assert evaluate("sqrt(16)") == 4
+    assert abs(evaluate("sin(0)")) < 1e-12
+    assert evaluate("max(1,2,3)") == 3
+    assert evaluate("min(1,2,3)") == 1
+    assert evaluate("abs(-7)") == 7
+
+def test_vars():
+    assert evaluate("x + pi", {"x": 3, "pi": math.pi}) == 3 + math.pi
+
+def test_errors():
+    for e in ["2 +", "1/0", "foo", "2 @ 3", "sqrt(-1)"]:
+        try:
+            evaluate(e)
+            raise AssertionError(f"no error for {e!r}")
+        except EvalError:
+            pass
+
+if __name__ == "__main__":
+    # run all test_ functions
+    import traceback
+    g = globals()
+    failed = 0
+    for name in sorted(n for n in g if n.startswith("test_")):
+        try:
+            g[name]()
+            print("PASS", name)
+        except Exception:
+            failed += 1
+            print("FAIL", name)
+            traceback.print_exc()
+    print("FAILED:", failed)
+    sys.exit(1 if failed else 0)