Finished the current assignments and lectures for my Programming Languages course on Coursera, so I figured I’d go and do some other stuff in ML. ML is a functional language, very heavy on recursion among other fun differences from imperative and OO languages.

Here’s a solution to Project Euler problem 1, summing all multiples of 3 and 5 that are below 1000.

fun sum_multiples_3_5(limit : int) =

if limit = 0

then 0

else if limit mod 3 = 0 orelse limit mod 5 = 0

then limit + sum_multiples_3_5(limit-1)

else sum_multiples_3_5(limit-1)

This is a general function, it will sum all multiples of 3 and 5 up through your limiting value. If you want less than 1000, then, you’d call it:

sum_multiples_3_5(999);

The answer, in this case, is 233168.

I may generalize it further, taking a list of ints which are the factors you want multiples of. That looks like a lot of extra work for something that is right now killing time because I can’t sleep, though, so I’ll be putting it off a bit.

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