Spreadsheet II

Requirements

• Export Spreadsheet as named and default. Expose set(cell, value), get(cell), and clear(cell). Cell addresses contain one or more letters followed by a positive row integer without leading zeros; trim surrounding whitespace and normalize letters to uppercase. Invalid addresses throw TypeError. Numeric values must be finite.
• set accepts a finite number or a formula string starting with = after trimming. Formulas contain decimal number literals or cell addresses separated by +, -, *, or /. Evaluate operators strictly left to right, without normal arithmetic precedence: =2+3*4 is 20. Whitespace between tokens is allowed.
• Decimal literals may have a leading minus and may use .5 or 2. forms. No whitespace is allowed between a numeric minus sign and its digits. Support subtraction of a negative literal, such as =1--2. No unary plus, negative cell reference, exponent notation, parentheses, ranges, functions, or implicit multiplication is required. Malformed formulas throw SyntaxError when set and leave any previous value unchanged.
• Missing or cleared cells read as 0. References are live: changing a dependency changes the next get result. Formula cells can reference other formulas, forward references, and repeated dependencies. Every get uses current state; memoization must not become a stale cache.
• Detect direct and indirect cycles during get and throw RangeError. Division by zero and any nonfinite intermediate result also throw RangeError. Validate formulas before committing writes, but defer dependency/cycle evaluation until get. After overwriting or clearing a cycle, valid reads must recover.
• Spreadsheet instances are independent. Return numeric results only; no UI, HTML, CSS, eval, Function constructor, external parser, strings as cell data, or ordinary precedence rules are required. Evaluate shared dependencies once per get call using a temporary memo.

Examples

Input: const s = new Spreadsheet(); s.set("A1", "=2+3*4"); s.get("A1");
Output: 20

Input: s.set("B1", 5); s.set("C1", "=B1/2-1"); s.get("C1"); s.set("B1", 9); s.get("C1");
Output: 1.5, then 3.5