Building a Ternary Operator

A common construct in programming languages is the ternary operator. Contrary to what the name implies, it cannot be implemented easily in Ryna with operators, since they are eager and the ternary operator is lazy. Let's take a look at how to implement it.

Syntax

The common syntax for the ternary operator is the following:

condition ? if_true : if_false

This syntax poses a problem, and it is that it makes the parser run out of memory. This is something that you might have to fight sometimes. This can easily be fixed by using delimiters:

{ condition ? if_true : if_false }

We can represent this syntax using the following NDL pattern:

"{" 
    {s} Arg(<expr>, condition) {s} "?" 
    {s} Arg(<expr>, if_true) {s} ":" 
    {s} Arg(<expr>, if_false) {s} 
"}"

Creating the macro

You can create the macro for the ternary operator using the following code (note that we have to escape the if's closing brace):

syntax ternary_operator from [...] {
    if $condition {
        return $if_true;
    \}

    return $if_false;
}

After this, you can write code such as this one:

let var = { 4 > 6 ? 1 + 2 : 1 + 4 };

Here, the 1 + 2 will never be executed, since the condition is false. The compiled code would be the following:

let var = do {
    if 4 > 6 {
        return 1 + 2;
    }

    return 1 + 4;
};