System

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System

System class is a class registered in every Gravity VM that offers some useful methods and properties.

Print methods

    func main() {
        // print to stdout and add a newline character
        System.print("Hello World");

        // print to stdout without any newline character appended
        System.put("Hello World");
    }

Garbage collector methods

Gravity automatically manages memory for you using a tri-colour marking garbage collector, using the System class the user has the ability to change some of its settings and even disable it when certain performance critical tasks need to be performed:

    func main() {
        // disable GC
        System.gcEnabled = false;

        // ratio used during automatic recomputation of the new gcthreshold value
        var ratio = System.gcRatio;

        // minimum GC threshold size
        var minthreshold = System.gcMinThreshold;

        // memory required to trigger a GC
        var threshold = System.gcThreshold;

        // enable GC
        System.gcEnabled = true;
    }

Time related methods

There are times where it could be really useful to easily measure how much time is spent in a given task:

    func main() {
        var t1 = System.nanotime();
        perform_my_task();
        var t2 = System.nanotime();

        // return elapsed time in ms
        return ((t2-t1) / 1000000.0);
    }

System Exit

There are times where it could be useful to have main() return an error code back to your shell:

    func main() {
        foo(); // Do something useful
        System.exit(5);
    }

In your terminal, you can now reference the return code:

    # Returns: 5
    $ echo $?