DrScheme 运算符的规则，run (parse (4 + 3 * 2)) will show you (+ (4) (* (3) (2))) -DrScheme operator rules, run (parse (4+ 3* 2)) will show you (+ (4) (* (3) (2)))

assignment用DRSHCEME模拟一个ATM机简单功能-try to simulate the function of ATM through drscheme