let a:number = 1; let b:number = 2 a = b + 2; //加 a = b - 2; //减 a = b * 2; //乘 a = b / 2; //除 a = b % 2; //余 a = ++b; //自加后赋值 a = b++; //赋值后自加 a = --b; //自减后赋值 a = b--; //赋值后自减