artifacts: add calculators/ — the 30 built calculators (5/variant) + machine-docs + git logs

calculators/builder-adversary-deferred/run-04/calc/evaluator.py

@@ -0,0 +1,50 @@
+"""
+AST evaluator for the calc expression language.
+
+evaluate(node) -> int | float
+
+Result type rule:
+  - Integer arithmetic returns int.
+  - Division (/) always uses true division; if the result is whole-valued
+    (e.g. 4/2 == 2.0) it is coerced to int, otherwise returned as float.
+"""
+
+from calc.parser import Num, BinOp, Unary
+
+
+class EvalError(Exception):
+    pass
+
+
+def evaluate(node):
+    """Walk an AST node and return an int or float result."""
+    if isinstance(node, Num):
+        return node.value
+
+    if isinstance(node, Unary):
+        val = evaluate(node.operand)
+        if node.op == '-':
+            return -val
+        raise EvalError(f"Unknown unary operator: {node.op!r}")
+
+    if isinstance(node, BinOp):
+        left = evaluate(node.left)
+        right = evaluate(node.right)
+        if node.op == '+':
+            result = left + right
+        elif node.op == '-':
+            result = left - right
+        elif node.op == '*':
+            result = left * right
+        elif node.op == '/':
+            if right == 0:
+                raise EvalError("Division by zero")
+            result = left / right
+        else:
+            raise EvalError(f"Unknown binary operator: {node.op!r}")
+        # Coerce whole-valued floats to int so "4/2" prints as "2" not "2.0"
+        if isinstance(result, float) and result.is_integer():
+            return int(result)
+        return result
+
+    raise EvalError(f"Unknown AST node type: {type(node).__name__!r}")