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

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

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+"""Recursive-descent parser for calc expressions.
+
+AST node shapes:
+  Num(value)              — numeric literal; value is int or float
+  BinOp(op, left, right)  — binary op; op is one of '+' '-' '*' '/'
+  Unary(op, operand)      — unary op; op is '-'
+
+All nodes implement __repr__ for easy shape inspection.
+
+Grammar (lowest → highest precedence):
+  expr    : term   (('+' | '-') term)*
+  term    : unary  (('*' | '/') unary)*
+  unary   : '-' unary | primary
+  primary : NUMBER | '(' expr ')'
+"""
+
+from __future__ import annotations
+from dataclasses import dataclass
+from typing import Union
+
+
+class ParseError(Exception):
+    pass
+
+
+@dataclass
+class Num:
+    value: Union[int, float]
+
+    def __repr__(self) -> str:
+        return f"Num({self.value!r})"
+
+
+@dataclass
+class BinOp:
+    op: str
+    left: "Node"
+    right: "Node"
+
+    def __repr__(self) -> str:
+        return f"BinOp({self.op!r}, {self.left!r}, {self.right!r})"
+
+
+@dataclass
+class Unary:
+    op: str
+    operand: "Node"
+
+    def __repr__(self) -> str:
+        return f"Unary({self.op!r}, {self.operand!r})"
+
+
+Node = Union[Num, BinOp, Unary]
+
+
+def parse(tokens: list) -> Node:
+    """Parse a token list into an AST. Raises ParseError on malformed input."""
+    p = _Parser(tokens)
+    tree = p.expr()
+    if p.current().kind != "EOF":
+        raise ParseError(f"unexpected token {p.current()!r} after expression")
+    return tree
+
+
+class _Parser:
+    def __init__(self, tokens: list) -> None:
+        self._tokens = tokens
+        self._pos = 0
+
+    def current(self):
+        return self._tokens[self._pos]
+
+    def consume(self, kind: str = None):
+        tok = self._tokens[self._pos]
+        if kind is not None and tok.kind != kind:
+            raise ParseError(
+                f"expected {kind!r} but got {tok.kind!r} ({tok.value!r})"
+            )
+        self._pos += 1
+        return tok
+
+    def expr(self) -> Node:
+        node = self.term()
+        while self.current().kind in ("PLUS", "MINUS"):
+            op = self.consume().value
+            node = BinOp(op, node, self.term())
+        return node
+
+    def term(self) -> Node:
+        node = self.unary()
+        while self.current().kind in ("STAR", "SLASH"):
+            op = self.consume().value
+            node = BinOp(op, node, self.unary())
+        return node
+
+    def unary(self) -> Node:
+        if self.current().kind == "MINUS":
+            self.consume("MINUS")
+            return Unary("-", self.unary())
+        return self.primary()
+
+    def primary(self) -> Node:
+        tok = self.current()
+        if tok.kind == "NUMBER":
+            self.consume("NUMBER")
+            return Num(tok.value)
+        if tok.kind == "LPAREN":
+            self.consume("LPAREN")
+            node = self.expr()
+            if self.current().kind != "RPAREN":
+                raise ParseError("unclosed '(' — expected ')'")
+            self.consume("RPAREN")
+            return node
+        if tok.kind == "EOF":
+            raise ParseError("unexpected end of input")
+        raise ParseError(f"unexpected token {tok.kind!r} ({tok.value!r})")