From the course: Programming Foundations: Discrete Mathematics
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Perform functions on lists
From the course: Programming Foundations: Discrete Mathematics
Perform functions on lists
- [Voiceover] Ok, now that we've seen how to create lists in SML, let's take a look at how to perform functions on lists. To do this, we're going to need to write our own new functions. Let's start by writing a function that finds the sum of all the items in a list. Here, I have a short list with some prime numbers. Let's write a function that will add all the numbers. I need to start by typing in "fun" to tell the interpreter i'm creating a new function. We'll call it "sum". Now in parentheses, I need to tell the interpreter what to expect. So i'm going to put two square brackets, open and closed, so that it knows to expect a list. I close my parentheses and now i have to give it a default value in case the user does not provide any elements in the list. In that case, I want the function just to return a zero. Ok we took care of that base case there. Now, I want to create a recursive process that will go through all the elements in the list. So i'm going to call "sum" again. I give a…
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