//1、直接赋值、不需要return返回
function resValue2() pure public returns(uint num1){
    num1 = 100;
}
//2、如果有return,以return为准,下面返回的是99
function resValue3() pure public returns(uint num1){
  num1 = 100;
  return 99;
}
//3、不return,也不赋值,那么为0
function resValue4() pure public returns(uint num1){
  uint b = 88;
}