Nested Function Expression Evaluator

Parse and evaluate nested function-style arithmetic expressions such as `add(2, mul(3, pow(4, 5)))`. The follow-up extends fixed-arity operators to variable-length argument lists. Requirements Input: a string expression using function-call syntax, e.g. add(1, sub(1, 0)) or add(2, mul(3, pow(4, 5))). Supported operators include add, subtract, multiply, divide, and exponentiation. Return the integer / numeric evaluation result. The expression can be nested arbitrarily deeply. Follow-up: support variable-length arguments, e.g. add(1, 2, 3, mul(4, 5, 6)). Examples add(1, sub(1, 0)) -> 2 add(2, mul(3, pow(4, 5))) -> 3074 Notes Tokenizer + recursive descent is the cleanest approach: parse operator, consume (, parse comma-separated child expressions, consume ), then evaluate. Iterative parsing works but is easy to make off-by-one errors under interview pressure; one candidate was specifically flagged for minor syntax and bounds issues. Clarify division behavior for negative values and non-divisible integers. Preparation Write a small tokenizer for identifiers, integers, commas, and parentheses. Practice a recursive parseExpr() that returns both the value and the next index. Drill the variable-arity follow-up by collecting arguments until ) instead of assuming exactly two.