Standard ml loop troubles

Question

I am setting up a function that will simulate a loop until a condition is met.

My overall plan is to use recursion but I am trying to get the basics down first.

I got a basic function working using an If statement that is seeing what the value of X is. I plan to use recursion to use X as an counter but I will get to that later.

My main concern right now is, it seems I can only do 1 command after the "then" statement.

fun whileloop (x,a) =
    if (x<4)
    then a+1 
    else a;

So this function works perfectly fine, but it seems the only command I can do is the a+1. If I try to perform any other command after that, before the else...it fails.

For example, the below code will fail on me.

fun whileloop (x,a) =
    if (x<4)
    then a+1 
    print "Testing"
    else a;

my ultimate goal is to create a loop that will perform several actions over and over until X reaches zero. I need to perform like 5-6 actions using different functions.

If you've received a complete answer and now have follow-up questions, you should ask them as new questions. — ruakh, Jun 04 '17 at 15:49
`a + 1` is not a "command", and doesn't actually *do* anything. There's no point evaluating `a + 1` and discarding the result. — ruakh, Jun 04 '17 at 15:50

score 0 · Accepted Answer · answered Jun 02 '17 at 08:45

0

You can evaluate several expressions in sequence using the semicolon operator:

( e1; e2; ...; eN )

For example,

fun iter n f = if n = 0 then () else (f n; iter (n-1) f)

answered Jun 02 '17 at 08:45

Andreas Rossberg

34,518
3
61
72

This helps with expressions yes, thank you very much. – Busta Jun 03 '17 at 15:22

Standard ml loop troubles

1 Answers1

Linked