39 lines
934 B
Rust
39 lines
934 B
Rust
pub type T = int;
|
|
pub const bits: uint = uint::bits;
|
|
|
|
/// Returns `base` raised to the power of `exponent`
|
|
pub fn pow(base: int, exponent: uint) -> int {
|
|
if exponent == 0u { return 1; } //Not mathemtically true if ~[base == 0]
|
|
if base == 0 { return 0; }
|
|
let mut my_pow = exponent;
|
|
let mut acc = 1;
|
|
let mut multiplier = base;
|
|
while(my_pow > 0u) {
|
|
if my_pow % 2u == 1u {
|
|
acc *= multiplier;
|
|
}
|
|
my_pow /= 2u;
|
|
multiplier *= multiplier;
|
|
}
|
|
return acc;
|
|
}
|
|
|
|
#[test]
|
|
fn test_pow() {
|
|
assert (pow(0, 0u) == 1);
|
|
assert (pow(0, 1u) == 0);
|
|
assert (pow(0, 2u) == 0);
|
|
assert (pow(-1, 0u) == 1);
|
|
assert (pow(1, 0u) == 1);
|
|
assert (pow(-3, 2u) == 9);
|
|
assert (pow(-3, 3u) == -27);
|
|
assert (pow(4, 9u) == 262144);
|
|
}
|
|
|
|
#[test]
|
|
fn test_overflows() {
|
|
assert (max_value > 0);
|
|
assert (min_value <= 0);
|
|
assert (min_value + max_value + 1 == 0);
|
|
}
|