if expressions

Let's say we want to know if an integer is even or odd, and display the answer. We can do something like this with pattern matching:

let parityMessage(n: Integer) :=
    case n % 2 do
        0 => String(n) + " is even!"
        1 => String(n) + " is odd!" 

It's fine, but I think it looks too complicated for a problem that should be simpler. Let's use an if expression:

let parityMessage(n: Integer) :=
    if n % 2 = 0 then
        String(n) + " is even!"
    else
        String(n) + " is odd!"

I think this is more explicit, and is less surprising when you read it. A nice thing about ifs in Komodo is that they are expressions themselves, so they return a result. You can do this:

let parityMessage(n: Integer) :=
    let text :=
        if n % 2 = 0 then
            " is even!"
        else
            " is odd!"
    
    String(n) + text

The thing with if expressions in Komodo is that you must write the else part. Always. Not doing it will result in an error when you try to execute the program.