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

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

@@ -0,0 +1,147 @@
+"""Recursive-descent parser for arithmetic expressions.
+
+AST node shapes (stable contract for the eval phase):
+  Num(value)              — numeric literal; value is int or float
+  BinOp(op, left, right) — binary operation; op in ('+', '-', '*', '/')
+  Unary(op, operand)     — unary operation; op == '-'
+
+Grammar (encodes precedence and left-associativity):
+  expr    → term   (('+' | '-') term)*
+  term    → unary  (('*' | '/') unary)*
+  unary   → '-' unary | primary
+  primary → NUMBER | '(' expr ')'
+"""
+
+from __future__ import annotations
+from typing import Union
+
+
+class ParseError(Exception):
+    pass
+
+
+class Num:
+    __slots__ = ("value",)
+
+    def __init__(self, value: Union[int, float]) -> None:
+        self.value = value
+
+    def __repr__(self) -> str:
+        return f"Num({self.value!r})"
+
+    def __eq__(self, other: object) -> bool:
+        return isinstance(other, Num) and self.value == other.value
+
+
+class BinOp:
+    __slots__ = ("op", "left", "right")
+
+    def __init__(self, op: str, left: "Node", right: "Node") -> None:
+        self.op = op
+        self.left = left
+        self.right = right
+
+    def __repr__(self) -> str:
+        return f"BinOp({self.op!r}, {self.left!r}, {self.right!r})"
+
+    def __eq__(self, other: object) -> bool:
+        return (
+            isinstance(other, BinOp)
+            and self.op == other.op
+            and self.left == other.left
+            and self.right == other.right
+        )
+
+
+class Unary:
+    __slots__ = ("op", "operand")
+
+    def __init__(self, op: str, operand: "Node") -> None:
+        self.op = op
+        self.operand = operand
+
+    def __repr__(self) -> str:
+        return f"Unary({self.op!r}, {self.operand!r})"
+
+    def __eq__(self, other: object) -> bool:
+        return (
+            isinstance(other, Unary)
+            and self.op == other.op
+            and self.operand == other.operand
+        )
+
+
+Node = Union[Num, BinOp, Unary]
+
+
+class _Parser:
+    def __init__(self, tokens: list) -> None:
+        self._tokens = tokens
+        self._pos = 0
+
+    def _peek(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}, got {tok.kind!r} ({tok.value!r})"
+            )
+        self._pos += 1
+        return tok
+
+    def parse(self) -> Node:
+        if self._peek().kind == "EOF":
+            raise ParseError("empty expression")
+        node = self._expr()
+        if self._peek().kind != "EOF":
+            tok = self._peek()
+            raise ParseError(
+                f"unexpected token {tok.kind!r} ({tok.value!r}) after expression"
+            )
+        return node
+
+    def _expr(self) -> Node:
+        node = self._term()
+        while self._peek().kind in ("PLUS", "MINUS"):
+            op = self._consume().value
+            right = self._term()
+            node = BinOp(op, node, right)
+        return node
+
+    def _term(self) -> Node:
+        node = self._unary()
+        while self._peek().kind in ("STAR", "SLASH"):
+            op = self._consume().value
+            right = self._unary()
+            node = BinOp(op, node, right)
+        return node
+
+    def _unary(self) -> Node:
+        if self._peek().kind == "MINUS":
+            op = self._consume().value
+            operand = self._unary()
+            return Unary(op, operand)
+        return self._primary()
+
+    def _primary(self) -> Node:
+        tok = self._peek()
+        if tok.kind == "NUMBER":
+            self._consume()
+            return Num(tok.value)
+        if tok.kind == "LPAREN":
+            self._consume("LPAREN")
+            node = self._expr()
+            if self._peek().kind != "RPAREN":
+                raise ParseError("unclosed parenthesis — expected ')'")
+            self._consume("RPAREN")
+            return node
+        if tok.kind == "EOF":
+            raise ParseError("unexpected end of expression")
+        raise ParseError(f"unexpected token {tok.kind!r} ({tok.value!r})")
+
+
+def parse(tokens: list) -> Node:
+    """Parse a token list produced by calc.lexer.tokenize into an AST."""
+    return _Parser(tokens).parse()