Fix Calculator Precision affecting Numeric evaluation (#338)

Author: devisettyharsha

src/strands_tools/calculator.py

@@ -378,10 +378,10 @@ def numeric_evaluation(result: Any, precision: int, scientific: bool) -> Union[i
         # For floating point, evaluate numerically
         if isinstance(result, sp.Basic):
             if hasattr(result, "is_real") and result.is_real:
-                float_result = float(result.evalf(precision))  # type: ignore
+                float_result = float(result.evalf())  # type: ignore
             else:
                 # Handle complex numbers
-                complex_result = complex(result.evalf(precision))  # type: ignore
+                complex_result = complex(result.evalf())  # type: ignore
                 return format_number(complex_result, scientific, precision)
         else:
             float_result = float(result)

tests/test_calculator_precision.py

@@ -0,0 +1,72 @@
+"""
+Regression tests for calculator precision handling.
+
+Precision must affect ONLY formatting, not numeric value.
+"""
+
+from strands_tools.calculator import calculator
+
+
+def extract_text(result):
+    assert result["status"] == "success"
+    return result["content"][0]["text"]
+
+
+# ------------------------------------------------------------
+# Core regression tests (original bug)
+# ------------------------------------------------------------
+
+def test_precision_does_not_change_real_value():
+    r2 = calculator("221 * 318.11", precision=2)
+    r4 = calculator("221 * 318.11", precision=4)
+
+    t2 = extract_text(r2)
+    t4 = extract_text(r4)
+
+    assert "70302.31" in t2
+    assert "70302.31" in t4   # trailing zeros are stripped by design
+
+
+def test_precision_does_not_change_division_value():
+    r2 = calculator("10 / 3", precision=2)
+    r6 = calculator("10 / 3", precision=6)
+
+    t2 = extract_text(r2)
+    t6 = extract_text(r6)
+
+    assert "3.33" in t2
+    assert "3.333333" in t6
+
+
+# ------------------------------------------------------------
+# Complex number regression tests
+# ------------------------------------------------------------
+
+def test_precision_does_not_change_complex_value():
+    r2 = calculator("(1 + I) * 318.11", precision=2)
+    r4 = calculator("(1 + I) * 318.11", precision=4)
+
+    t2 = extract_text(r2)
+    t4 = extract_text(r4)
+
+    assert "318.11" in t2
+    assert "318.11" in t4
+
+
+# ------------------------------------------------------------
+# Symbolic guardrails (correct semantics)
+# ------------------------------------------------------------
+
+def test_expression_with_symbols_remains_symbolic():
+    r = calculator("x + 1", precision=2)
+    t = extract_text(r)
+
+    assert "x + 1" in t
+
+
+def test_force_numeric_applies_numeric_evaluation():
+    r = calculator("sqrt(2)", precision=4, force_numeric=True)
+    t = extract_text(r)
+
+    assert "1.4142" in t
+