Java Long Number Mod mod(long v, long m)

Description

Returns v (mod m).
The value returned lies in range [ 0 ..

License

Open Source License

Parameter

Parameter	Description
v	a value
m	a modulus

Return

v (mod m), or if m = 0

Declaration

public static long mod(long v, long m) 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

public class Main {
    /**//ww w .j  av  a  2 s.com
     * Some methods return this value as indication that the answer doesn't exist or is undefined.<br>
     * For example, when mod = 0 in modular arithmetics, or when a number isn't a perfect power and
     * a function should return its base.
     * <p>This constant equals to {@code Integer.MIN_VALUE} because {@code Integer.MIN_VALUE}
     * can't be a base of any perfect power that fits in long. Proof:<ul>
     * <li>Base of perfect square is a positive number.</li>
     * <li>Integer.MIN_VALUE<sup>3</sup> = ((-2)<sup>31</sup>)<sup>3</sup> = (-2)<sup>93</sup> &lt; (-2)<sup>63</sup> = Long.MIN_VALUE.</li>
     * <li>Higher powers would give higher values.</li></ul>
     * So no power greater than one can return base = {@code Integer.MIN_VALUE} for any long integer.
     * <p>Also, any modular arithmetic operation returns non-negative value,
     * so negative values can be used as error codes.
     * <p>Error codes are more desirable than throwing an exception when performance matters.
     */
    public static final int NOT_FOUND = Integer.MIN_VALUE;

    /**
     * Returns v (mod m).<br>
     * The value returned lies in range [ 0 .. |m| - 1 ].<br>
     * mod( x, m ) = mod( x, -m ).<br>
     * This method differs from v % m in that it always returns non-negative value.<br>
     * If m = 0 then {@link #NOT_FOUND} is returned.
     * @param v a value
     * @param m a modulus
     * @return v (mod m), or {@link #NOT_FOUND} if m = 0
     */
    public static int mod(int v, int m) {
        if (m == 0)
            return NOT_FOUND;
        v %= m;
        if (v < 0) {
            // Note: if m = Integer.MIN_VALUE then addition behaves exactly like subtraction.
            if (m < 0)
                v -= m;
            else
                v += m;
        }
        return v;
    }

    /**
     * Returns v (mod m).<br>
     * The value returned lies in range [ 0 .. |m| - 1 ].<br>
     * mod( x, m ) = mod( x, -m ).<br>
     * This method differs from v % m in that it always returns non-negative value.<br>
     * If m = 0 then {@link #NOT_FOUND} is returned.
     * @param v a value
     * @param m a modulus
     * @return v (mod m), or {@link #NOT_FOUND} if m = 0
     */
    public static long mod(long v, long m) {
        if (m == 0L)
            return NOT_FOUND;
        v %= m;
        if (v < 0L) {
            // Note: if m = Long.MIN_VALUE then addition behaves exactly like subtraction.
            if (m < 0L)
                v -= m;
            else
                v += m;
        }
        return v;
    }
}

Related

1. mod(long a, long b)
2. mod(long pNum, long pDivisor)
3. mod(long x, long y)
4. modDivide(long a, long b, long m)
5. modifiedCalcElementOffset(long index, long mask)
6. modifyValue(long value, char op, long modifier, long max, long min)