String Formatting

This section describes how to use the format() command to format strings.

Background

Normally, strings are concatenated by using addition (+) between strings. Such as:

    string s = "Hello" + " World";

When you want to include a different type it must be cast to a string first, which can make the code more complicated and harder to follow.

    i32 x, y = 5, 20;
    string location = "Location = " + x as string + ", " + y as string;

format()

The format function makes this much easier. Each input parameter is concatenated and automatically casted to a string if needed.

    string location = format("Location = ", x, ", ", y);

Format also allows injecting code from inside the string. When you use this feature the compiler simply reformats it into the expanded form.

    string location = format("Location = {x}, {y}"); // same as below

    // compiler converts the above into this form automatically.
    string location = format("Location = ", x, ", ", y);

You can also leave the braces { } empty and the compiler will look ahead and grab the next parameter. This is a convenience but it can become confusing if you mix it with parameter concatenation.

    // All of these have the same result: "Location = 5, 20".
    // x and y added directly
    string location = format("Location = {x}, {y}");

    // y added using concatenation
    string location = format("Location = {x}, ", y);

    // x and y added using look ahead
    string location = format("Location = {}, {}", x, y);

    // x added using look ahead, y added directly
    string location = format("Location = {}, {y}", x);

    // x and y added using concatenation
    string location = format("Location = ", x, ", ", y);

    // x and y added using look ahead
    string location = format("Location = {}", x, ", {}", y);

All of these features are also present when using the print() and println() commands.

    println("Location = " + x as string + ", " + y as string);
    println(format("Location = {x}, {y}"));  // same as above
    println("Location = {x}, {y}");          // same as above