2018-12-26 定义一个过程，它以三个数为参数，返回其中较大的两个数之和

问：定义一个过程，它以三个数为参数，返回其中较大的两个数之和
解：

(define min(a b)
    (if (< a b) a b)
)

(define minnum(a b c)
    (min(min a b) c)
)

(define sumbig( a b c)
    (
        COND(= a minnum(a b c ))
            (+ b c)
        COND(= b minnum(a b c ))
            (+ a c)
        COND(= c minnum(a b c ))
            (+ a b)

    )
)