Spreadsheet

Requirements

• Export Spreadsheet as named and default. Implement set(cell, value), get(cell), and clear(cell). set and clear return undefined; get returns a numeric value.
• Cell addresses are letters followed by a positive row number, such as A1 or AA12, case-insensitive with optional outer whitespace. Normalize addresses to uppercase. Invalid addresses throw TypeError.
• set accepts a finite number or an addition-formula string beginning with =. Formulas contain one or more terms separated by +, with whitespace allowed. A term is a cell address or a finite decimal literal, optionally negative. Exponents, subtraction operators, parentheses, ranges, and other functions are outside scope.
• Examples of valid terms include 2, -2.5, .5, and A1. Invalid formula strings throw SyntaxError without replacing the existing cell. Non-finite numeric cell values throw TypeError.
• Unset or cleared cells evaluate to 0. Formula references are live: later changes to referenced numbers or formulas affect get immediately. Repeated references count each time; dependent formulas may form a graph.
• Detect direct or indirect circular dependencies during get and throw RangeError. A formula sum that becomes non-finite also throws RangeError. A later edit or clear can repair a cycle.
• Keep instances independent. Memoization within one get is allowed, but stale cross-call cached values are not. Do not use eval or Function, mutate caller input, or build a spreadsheet UI.

Examples

Input: const sheet = new Spreadsheet();
sheet.set("A1", 3);
sheet.set("B1", "=A1 + 2.5");
sheet.get("B1");
Output: 5.5

Input: sheet.set("A1", 10);
sheet.get("B1");
sheet.clear("A1");
sheet.get("B1");
Output: 12.5 after editing A1, then 2.5 after clearing it.