Question

I have to create the following:
A Scheme procedure named ‘proc2’ which takes 4 numbers as arguments
and returns the value of the largest argument minus the smallest.

So I want to write
(define proc2
lambda(a b c d)
…
)

Is there any way I can evaluate (> a b), (> a c), (> a d) at the same time? I want to get the largest (and the smallest)number without having to write nested ifs.

Answer 1

Can you use the max and min procedures? if the answer is yes, it’s pretty simple:

(- (max a b c d) (min a b c d))

If not, remember that <, >, <=, >= accept a variable number of arguments, so this is valid code and will tell you if a is smaller than b and b is smaller than c and c is smaller than d (although you’ll have to test more combinations of b, c, d to make sure that a is the smallest value).

(< a b c d)

Also remember to consider the cases when two or more numbers are equal (that’s why it’s a good idea to use <= instead of <).

Anyway, you’ll have to use conditionals. Maybe nested ifs, or perhaps a cond to make things simpler – you can work out the details yourself, I’m guessing this is homework.