adamchalmers

import Foundation

// Represents a calculation that could either succeed, or fail with an error message.
enum Result<A> {
    
    // If the calculation was successful, store the result.
    case Ok(A)
    // If the calculation failed, store the error message.
    case Err(String)
    

adamchalmers

func extend<T: Collection, U: Collection>(_ base: T, withNewElems: U) -> [T.Iterator.Element]
    where T.Iterator.Element == U.Iterator.Element,
          T.Iterator.Element: Equatable {
        let newElems = withNewElems.filter { !base.contains($0) }
        return Array(base) + newElems
}

adamchalmers

func extend<T: Collection, U: Collection>(_ base: T, withNewElems: U) -> [T.Iterator.Element]
    where T.Iterator.Element == U.Iterator.Element {
        let newElems = withNewElems.filter { !base.contains($0) }
        return Array(base) + newElems
}

adamchalmers

func extend<T: Collection, U: Collection>(_ base: T, withNewElems: U)
    where T.Iterator.Element == U.Iterator.Element {
        // function body will go here
        // also ignoring return type for now
}

adamchalmers

func extend<T: Collection, U: Collection>(_ base: T, withNewElems: U)

adamchalmers

func extend<T: Collection>(_ base: T, withNewElems: T) -> T {
    // Ignore the function body for now, 
    // we’re just trying to make it compile.
    return base
}

adamchalmers

func extend<T>(_: Collection, withNewElems: Collection) -> [T]

adamchalmers

func extend<T>(_: [T], withNewElems: [T]) -> [T]

adamchalmers

let array = Array(0..<10)
let slice = array[2..<5]

// Mixing Array/ArraySlice compiles!
print(extend(array, withNewElems: array))
print(extend(array, withNewElems: slice))
print(extend(slice, withNewElems: slice))

// Mixing Ints/Bools doesn't compile!
print(extend(array, withNewElems: [true, false]))

adamchalmers

use std::ffi::OsStr;
use std::io;
use std::fs::{self};
use std::path::{Path, PathBuf};

// Find all files in the given directory with the given extension
fn paths_matching(extension: &str, dir: &Path) -> io::Result<Vec<PathBuf>> {
    let mut paths: Vec<PathBuf> = Vec::new();
    for entry in fs::read_dir(dir)? {
        let entry = entry?;