Math.sol

pragma solidity ^0.4.0;

/*
#    Copyright (C) 2017  alianse777

#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/


contract Math{
   /**
    * @dev Compute square root of x
    * @param x 
    * @return sqrt(x)
    */
   function sqrt(uint x) internal pure returns (uint){
       uint n = x / 2;
       uint lstX = 0;
       while (n != lstX){
           lstX = n;
           n = (n + x/n) / 2; 
       }
       return uint(n);
   }
	
    /**
     * @dev Compute modular exponential (x ** k) % m
     * @param x k m
     * @return uint
     */
   function mexp(uint x, uint k, uint m) internal pure returns (uint r) {
       r = 1;
       for (uint s = 1; s <= k; s *= 2) {
           if (k & s != 0) r = mulmod(r, x, m);
            x = mulmod(x, x, m);
       }
    }
    
    function abs(int x) internal pure returns (uint) {
        if(x < 0) {
            return uint(-x);
        }
        return uint(x);
    }
    
    function u_pow(uint x, uint p) internal pure returns (uint) {
        if(p == 0) return 1;
        if(p % 2 == 1) {
            return u_pow(x, p-1)*x;
        }
        else
        {
            return u_pow(x, p / 2)*u_pow(x, p / 2);
        }
    }
    
    function pow(int x, uint p) internal pure returns (int) {
        int r = int(u_pow(abs(x), p));
        if(p % 2 == 1) {
            return -1*r;
        }
        return r;
    }
}