ethereum(以太坊)(六)--整型(int)

pragma solidity ^0.4.20;

/*
uint8 uint16 ...uint256
int8  int16 int24 ..int256

uint => uint256
int  =>  int256

int8 有符号 +1 ,-3
uint 无符号 1,2

int8 8(位)
111 1111 ~ 0 111 1111
- (1+2+4+8+16+32+64) ~ + (1+2+4+8+16+32+64)
-127 ~ 127  255（127*2+0）

uint8
0000 ~ 1111 1111 (0~255)
*/

contract Random{

    uint randNonce;

    function getRand() public returns(uint){
　　　　　// randint:0 - 99
        uint id = uint(keccak256(abi.encodePacked(randNonce,now,msg.sender))) % 100;
        randNonce ++;
        return id;
    }

    uint8 a = 3;
    uint8 b = 7;

    function yu() view public returns(uint8) {
        return a & b;
        // 0000 0011
        // 0000 0111

        // 0000 0011 = 3
    }

    function huo() view public returns(uint8) {
        return a | b;
        // 0000 0111 = 7
    }

    function yihuo() view public returns(uint8) {
        return a ^ b;
        // 0000 0100 = 4
    }

    function fei() view public returns(uint8) {
        return ~b;
        // 1111 1000 =255-7 = 248
    }

    function add() view public returns(uint) {
        return a + b ; //
    }

    function sub() view public returns(uint) {
        return a - b ; //-4 + 256 = 252
    }

    function mul() view public returns(uint) {
        return a * b ; //
    }

    function div() view public returns(uint) {
        return b / a ; //
    }

    function mod() view public returns(uint) {
        return b % a ; //
    }

    function mi() view returns(uint){
        return b ** a; //343 - 256 = 87
    }

    function leftshit() view returns(uint){
        return b << a;
        // 0000 0111
        // 0011 1000 = 56
    }

    function rigthshit() view returns(uint){
        return b >> a;
        // 0000 0111 = 0
    }
}