Factorial — canonical big.Int example
fact := big.NewInt(1)
for i := int64(1); i <= 100; i++ {
fact.Mul(fact, big.NewInt(i))
}
fmt.Println(fact.String())math/big
Arbitrary-precision integers (Int), rationals (Rat), and floats (Float). No overflow, at the cost of allocation.
Int — arbitrary-precision integers
Go operators don't work — you call methods that write into a receiver. The result is always the receiver, which is returned for chaining.
Modular exponentiation for crypto-ish math
result := new(big.Int).Exp(base, exp, mod)Parse from a string
n, ok := new(big.Int).SetString("123456789012345678901234567890", 10)
fmt.Println(n, ok)Rat — arbitrary-precision rationals
Exact fractions
r := big.NewRat(1, 3)
r.Add(r, big.NewRat(1, 6))
fmt.Println(r.String()) // 1/2Float — arbitrary-precision floating-point
High-precision math
f := new(big.Float).SetPrec(200).SetFloat64(1.0)
f.Quo(f, big.NewFloat(7))
fmt.Println(f.Text('f', 50))