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Switch Statements

Switch statements in Spice can be used to execute different code paths based on the value of a variable. This is similar to switch statements in other languages, but with some differences. The expression in the switch statement can be of type int, long, short, byte, char or bool and the individual match expressions need to be literals of the respective type.

Usage

Here's a simple example for an switch statement:

switch number {
    case 0: { printf("Zero"); }
    case 1: { printf("One"); }
    case 2: { printf("Two"); }
    case 3: { printf("Three"); }
    case 4: { printf("Four"); }
    case 5: { printf("Five"); }
    case 6: { printf("Six"); }
    case 7: { printf("Seven"); }
    case 8: { printf("Eight"); }
    case 9: { printf("Nine"); }
    default: { printf("NaN"); }
}
Each case branch gets executed, if the value of the switch statement matches the value of the case branch. If no case branch matches, the optional default branch gets executed. The default branch must be the last branch in the switch statement, the order of case branches does not matter.

Optional parentheses

As with the for, foreach and while loops, the parentheses around the head of the switch statement are optional.

Let's take a look at a switch statement:

switch (input) {
    case 0, 2, 4, 6, 8: { printf("Even"); }
    case 1, 3, 5, 7, 9: { printf("Odd"); }
}
This piece of code is a bit pointless, but you can see, that you can also assign two constant values to result in the same branch being executed.

Fallthrough

In Spice, the switch statement does not fall through by default. This means, that you don't need to use the break keyword to prevent the next case from being executed, like in other languages. In Spice, you have to use the fallthrough keyword to fall through to the next case branch. This originated from the assumption, that you more often want to execute one branch, instead of having fallthrough behavior.

The fallthrough keyword can be used like this:

int i = 1;
switch i {
    case 1, 2: {
        printf("1 or 2\n");
        fallthrough;
    }
    case 6, 9: {
        printf("6 or 9\n");
    }
    default: {
        printf("Default\n");
    }
}
The fallthrough keyword ensures that in the above example, the case 6, 9 branch gets executed, even though the value of i is 1 or 2 and the respective branch was executed beforehand.