Chapter 3.2: Walk and While

Loops

When you need to run a block of code multiple times, you use a loop. Loops let your program “cycle” through code, whether that’s repeating an action x number of times or continuing until a condition changes.

GLang gives you two main ways to loop: while and walk.

while

A while loop is basically an if statement that keeps running while a condition remains true. If that condition never becomes false, your loop will run forever (and probably melt your computer’s hardware!)

while true {
    bark("This loop runs forever!!!");
}

Of course, infinite loops aren’t always bad, sometimes you want your program to keep running until something happens. For example, you might want to increment a value until it hits a goal.

obj x = 0;

while x != 100 {  # stops when x == 100
    x = x + 1;
}

A classic example may be a game loop that runs while the game is active:

while game_is_running() {
    render_opponent();
    render_player();
}

Range Loops: walk

The walk loop gives you more control. Instead of looping until some condition changes, you define exactly how many times it should run.

walk i = 0 through 10 {
    bark(i);
}

i starts at 0, and the loop runs while i is less than 10. Each time through, i increases by 1 automatically.

Therefore, this outputs: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 in the terminal.

You can also control how much i increases each time with the optional step keyword:

walk i = 0 through 10 step = 2 {
    bark(i); # outputs 0, 2, 4, 6, 8
}

Iterator Loops: walk

The walk loop also gives you the ability to loop through an object (often called an iterator)

obj my_list = [1, 2, 3];

walk i through my_list {
    bark(i); # outputs 1, 2, 3 (each element in the list)
}

Each time through the loop, i is set to the next element in the iterator. Both the list and string type are iterators, meaning you can also loop through the characters in a string too:

obj string = "hello";

walk i through string {
    bark(i); # outputs h, e, l, l, o (each character in the string)
}

Your Challenge 🤔

Use a walk loop to output numbers 0 through 10000 counting by 100s (0, 100, 200, and so on...)

Answer

walk i = 0 through 10000 step = 100 {
    bark(i);
}