Exact arithmetic on fractions — simplify, add, subtract, multiply, divide, and convert between improper fractions, mixed numbers, and decimals. Uses BigInt so huge numerators stay precise. Type fractions as 3/4, mixed numbers as 1 2/3, or plain integers/decimals.
Accepted formats: 3/4, -5/6, 1 2/3 (mixed), 0.125, 42.
Fractions are normalized so the denominator is always positive, then reduced to lowest terms with the Euclidean algorithm on BigInt. Decimal inputs like 0.125 are treated as 125/1000, so there's no floating-point drift. Division by zero throws; improper fractions convert cleanly to mixed numbers.