Statements

Statements largely work like in C, but with some additions.

Labelled break and continue

Labelled break and continue lets you break out of an outer scope. Labels can be put on if, switch, while and do statements.

fn void test(int i)
{
    if FOO: (i > 0)
    {
        while (1)
        {
            io::printfn("%d", i);
            // Break out of the top if statement.
            if (i++ > 10) break FOO;
        }
    }
}

Do-without-while

Do-while statements can skip the ending while. In that case it acts as if the while was while(0):

The function below prints World! if x is zero, otherwise it prints Hello World!.

fn void test(int x)
{
    do
    {
        if (!x) break;
        io::printf("Hello ");
    };
    io::printf("World!\n");
}

Nextcase and labelled nextcase

The nextcase statement is used in switch and if-catch to jump to the next statement:

switch (i)
{
    case 1:
        doSomething();
        nextcase; // Jumps to case 2
    case 2:
        doSomethingElse();
}

It’s also possible to use nextcase with an expression, to jump to an arbitrary case or between labeled switch statements:

switch MAIN: (enum_var)
    case FOO:
        switch (i)
        {
            case 1:
                doSomething();
                nextcase 3; // Jump to case 3
            case 2:
                doSomethingElse();
            case 3:
                nextcase rand(); // Jump to random case
            default:
                io::printn("Ended");
                nextcase MAIN: BAR;  // Jump to outer (MAIN) switch
        }
    case BAR:
        io::printn("BAR");
    default:
        break;
}

Which can be used as structured goto when creating state machines.

Switch cases with runtime evaluation

It’s possible to use switch as an enhanced if-else chain:

switch (true)
{
    case x < 0:
        xless();
    case x > 0:
        xgreater();
    default:
        xequals();
}

The above would be equivalent to writing:

if (x < 0)
{
    xless();
}
else if (x > 0)
{
    xgreater();
}
else
{
    xequals();
}

Note that because of this, the first match is always picked. Consider:

switch (true)
{
    case x > 0:
        foo();
    case x > 2:
        bar();
}

Because of the evaluation order, only foo() will be invoked for x > 0, even when x is greater than 2.

It’s also possible to omit the conditional after switch. In that case it is implicitly assumed to be same as writing (true)

switch
{
    case foo() > 0:
        bar();
    case test() == 1:
        baz();
}

Jumptable switches with @jump

Regular switch statements with only enum or integer cases may use the @jump attribute. This attribute ensures that the switch is implemented as a jump using a jumptable. In C this is possible to do manually using labels and calculated gotos which are extensions available in GCC/Clang.

The behaviour of the switch itself does not change with a jumptable, but some restrictions will apply. Typically used for situations like bytecode interpreters, it might perform worse or better than a regular switch depending on the situation. nextcase statements will also use jumptable dispatch when @jump is used.