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

calculators/builder-solo/run-04/calc/evaluator.py

@@ -0,0 +1,40 @@
+"""AST evaluator for calc expressions.
+
+evaluate(node) -> int | float
+
+Result-type rule:
+  - Whole-valued results (including float 2.0) are returned/displayed as int.
+  - Non-whole results are returned as float.
+  Division by zero raises EvalError, not a bare ZeroDivisionError.
+"""
+
+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):
+        if node.op == "-":
+            return -evaluate(node.operand)
+        raise EvalError(f"unknown unary op {node.op!r}")
+    if isinstance(node, BinOp):
+        left = evaluate(node.left)
+        right = evaluate(node.right)
+        if node.op == "+":
+            return left + right
+        if node.op == "-":
+            return left - right
+        if node.op == "*":
+            return left * right
+        if node.op == "/":
+            if right == 0:
+                raise EvalError("division by zero")
+            result = left / right
+            return int(result) if result == int(result) else result
+        raise EvalError(f"unknown binary op {node.op!r}")
+    raise EvalError(f"unknown node type {type(node).__name__}")