問：定義一個(gè)過程，它以三個(gè)數(shù)為參數(shù)，返回其中較大的兩個(gè)數(shù)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)

    )
)