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

calculators/builder-solo/run-02/calc/evaluator.py

@@ -0,0 +1,41 @@
+"""Evaluator for the arithmetic AST produced by calc.parser.
+
+evaluate(node) -> int | float
+
+Result-type rule: if the result is a whole number (no fractional part),
+return an int; otherwise return a float.  This means 4/2 → 2 (int) and
+7/2 → 3.5 (float).
+"""
+
+from calc.parser import Num, BinOp, Unary, Node
+
+
+class EvalError(Exception):
+    pass
+
+
+def evaluate(node: Node) -> "int | float":
+    if isinstance(node, Num):
+        return node.value
+    if isinstance(node, Unary):
+        return -evaluate(node.operand)
+    if isinstance(node, BinOp):
+        left = evaluate(node.left)
+        right = evaluate(node.right)
+        op = node.op
+        if op == '+':
+            result = left + right
+        elif op == '-':
+            result = left - right
+        elif op == '*':
+            result = left * right
+        elif op == '/':
+            if right == 0:
+                raise EvalError("division by zero")
+            result = left / right
+        else:
+            raise EvalError(f"unknown operator: {op!r}")
+        if isinstance(result, float) and result.is_integer():
+            return int(result)
+        return result
+    raise EvalError(f"unknown node type: {type(node).__name__}")