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

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

@@ -0,0 +1,48 @@
+"""Evaluator for the arithmetic AST produced by calc.parser.
+
+evaluate(node) -> int | float
+
+Whole-valued results are returned as int ("4/2" -> 2).
+Non-whole results are returned as float ("7/2" -> 3.5).
+Division by zero raises EvalError.
+"""
+from __future__ import annotations
+
+from calc.parser import Node, Num, BinOp, Unary
+
+
+class EvalError(Exception):
+    pass
+
+
+def _normalize(val: int | float) -> int | float:
+    """Return int if val is a whole-valued float, otherwise unchanged."""
+    if isinstance(val, float) and val.is_integer():
+        return int(val)
+    return val
+
+
+def evaluate(node: Node) -> int | float:
+    """Walk an AST node and return its numeric value."""
+    if isinstance(node, Num):
+        return node.value
+    if isinstance(node, BinOp):
+        l = evaluate(node.left)
+        r = evaluate(node.right)
+        if node.op == '+':
+            return _normalize(l + r)
+        if node.op == '-':
+            return _normalize(l - r)
+        if node.op == '*':
+            return _normalize(l * r)
+        if node.op == '/':
+            if r == 0:
+                raise EvalError("division by zero")
+            return _normalize(l / r)
+        raise EvalError(f"unknown operator {node.op!r}")
+    if isinstance(node, Unary):
+        val = evaluate(node.operand)
+        if node.op == '-':
+            return _normalize(-val)
+        raise EvalError(f"unknown unary operator {node.op!r}")
+    raise EvalError(f"unknown AST node type {type(node).__name__!r}")