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

calculators/builder-solo/run-03/calc/evaluator.py

@@ -0,0 +1,39 @@
+from calc.parser import Num, Unary, BinOp, Node
+
+
+class EvalError(Exception):
+    pass
+
+
+def evaluate(node: Node):
+    """Walk the AST and return an int or float.
+
+    Result-type rule: if the result is mathematically whole-valued it is
+    returned as int; non-whole results are returned as float.  This rule is
+    applied after every operation so intermediate values are also normalised.
+    """
+    if isinstance(node, Num):
+        return _normalise(node.value)
+    if isinstance(node, Unary):
+        return _normalise(-evaluate(node.operand))
+    if isinstance(node, BinOp):
+        left = evaluate(node.left)
+        right = evaluate(node.right)
+        if node.op == '+':
+            return _normalise(left + right)
+        if node.op == '-':
+            return _normalise(left - right)
+        if node.op == '*':
+            return _normalise(left * right)
+        if node.op == '/':
+            if right == 0:
+                raise EvalError("division by zero")
+            return _normalise(left / right)
+    raise EvalError(f"unknown node type: {type(node).__name__}")
+
+
+def _normalise(value):
+    """Return int when value is whole-valued, float otherwise."""
+    if isinstance(value, float) and value == int(value):
+        return int(value)
+    return value