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

calculators/builder-solo/run-05/calc/parser.py

@@ -0,0 +1,118 @@
+"""Recursive-descent parser for arithmetic expressions.
+
+Grammar (precedence low→high):
+  expr   ::= term   ( ('+' | '-') term   )*
+  term   ::= factor ( ('*' | '/') factor )*
+  factor ::= NUMBER | '(' expr ')' | '-' factor
+
+AST node shapes (all dataclasses):
+  Num(value)              — numeric leaf; value is int or float
+  BinOp(op, left, right)  — op in ('+', '-', '*', '/'), children are nodes
+  Unary(op, operand)      — op is '-', operand is a node
+"""
+
+from dataclasses import dataclass
+from typing import Any
+
+from calc.lexer import Token, tokenize
+
+
+class ParseError(Exception):
+    pass
+
+
+@dataclass
+class Num:
+    value: Any
+
+    def __repr__(self):
+        return f"Num(value={self.value!r})"
+
+
+@dataclass
+class BinOp:
+    op: str
+    left: Any
+    right: Any
+
+    def __repr__(self):
+        return f"BinOp(op={self.op!r}, left={self.left!r}, right={self.right!r})"
+
+
+@dataclass
+class Unary:
+    op: str
+    operand: Any
+
+    def __repr__(self):
+        return f"Unary(op={self.op!r}, operand={self.operand!r})"
+
+
+class _Parser:
+    def __init__(self, tokens: list):
+        self._tokens = tokens
+        self._pos = 0
+
+    def _peek(self) -> Token:
+        return self._tokens[self._pos]
+
+    def _consume(self) -> Token:
+        tok = self._tokens[self._pos]
+        self._pos += 1
+        return tok
+
+    def _expect(self, kind: str) -> Token:
+        tok = self._peek()
+        if tok.kind != kind:
+            raise ParseError(f"Expected {kind} but got {tok.kind!r}")
+        return self._consume()
+
+    def parse(self):
+        node = self._expr()
+        if self._peek().kind != 'EOF':
+            raise ParseError(f"Unexpected token {self._peek()!r}")
+        return node
+
+    def _expr(self):
+        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 = self._factor()
+        while self._peek().kind in ('STAR', 'SLASH'):
+            op = self._consume().value
+            right = self._factor()
+            node = BinOp(op, node, right)
+        return node
+
+    def _factor(self):
+        tok = self._peek()
+
+        if tok.kind == 'NUMBER':
+            self._consume()
+            return Num(tok.value)
+
+        if tok.kind == 'LPAREN':
+            self._consume()
+            node = self._expr()
+            self._expect('RPAREN')
+            return node
+
+        if tok.kind == 'MINUS':
+            self._consume()
+            operand = self._factor()
+            return Unary('-', operand)
+
+        if tok.kind == 'EOF':
+            raise ParseError("Unexpected end of input")
+
+        raise ParseError(f"Unexpected token {tok!r}")
+
+
+def parse(tokens: list):
+    """Parse a token list (from tokenize()) into an AST. Raises ParseError on bad input."""
+    return _Parser(tokens).parse()