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sqrt_int

sqrt.sqrt_int

fn sqrt_int(comptime T: type, value: T) Sqrt(T)

File

lib/std/math/sqrt.zig:36

Code

fn sqrt_int(comptime T: type, value: T) Sqrt(T) {
    if (@typeInfo(T).int.bits <= 2) {
        return if (value == 0) 0 else 1; // shortcut for small number of bits to simplify general case
    } else {
        const bits = @typeInfo(T).int.bits;
        const max = math.maxInt(T);
        const minustwo = (@as(T, 2) ^ max) + 1; // unsigned int cannot represent -2
        var op = value;
        var res: T = 0;
        var one: T = 1 << ((bits - 1) & minustwo); // highest power of four that fits into T

        // "one" starts at the highest power of four <= than the argument.
        while (one > op) {
            one >>= 2;
        }

        while (one != 0) {
            const c = op >= res + one;
            if (c) op -= res + one;
            res >>= 1;
            if (c) res += one;
            one >>= 2;
        }

        return @as(Sqrt(T), @intCast(res));
    }
}