owensd

    int foo(int bar):
      // network call here
      // write a log to disk here
      // change a global value here

      return happy_int

    f(x, y) = z

    f :: [a] -> a

    let r = f([...])
    assert(r, correct_value)
    assert(r.type, correct_type)

    1. x <= TYPE_MAX (for free in a statically typed system)
    2. x <= TYPE_MAX - y
    3. y <= TYPE_MAX (for free in a statically typed system)
    4. y <= TYPE_MAX - x

    1. x power of 2
    2. y power of 2

    def add(x, y)
      assert x is int
      assert y in int

      return x + y

    // test cases
    assertIsThrown(add("foo", "bar"))

    add((short)0, (long)1)   // compiler error if you have an extremely rigid type system

    // some collection we are holding the values in for some reason
    NSMutableArray *inputValues = [[NSMutableArray alloc] init];

    NSString *someInputValue = // probably read from user input or a file
    NSInteger value = [someInputValue integerValue];

    BOOL validInput = YES;
    if (value == 0) { // we need to check that there really is a value of 0...
        NSString *trimmed = [someInputValue stringByTrimmingCharactersInSet:NSCharacterSet.whitespaceCharacterSet];
        NSString *trimmed0 = [trimmed stringByTrimmingCharactersInSet:[NSCharacterSet characterSetWithCharactersInString:@"0"]];
        if (trimmed0.length != 0) {
            // oops, actually had an error... handle it
            validInput = NO;
        }
    }
    
    if (validInput) {
        [inputValues addObject:@(value)];
    }