/* parse C comments interactively, using events and a state machine */
main()
{
    state plain;
}
@keypressed(key) <plain>
{
    state (key == '/') slash;
    if (key != '/') {
        echo key;
    }
}
@keypressed(key) <slash>
{
    state (key != '/') plain;
    state (key == '*') comment;
    echo '/';    /* print '/' held back from previous state */
    if (key != '/') {
        echo key;
    }
}
@keypressed(key) <comment>
{
    echo key;
    state (key == '*') star;
}
@keypressed(key) <star>
{
    echo key;
    state (key != '*') comment;
    state (key == '/') plain;
}
echo(key) <plain, slash>
{
    printchar key, yellow;
}
echo(key) <comment, star>
{
    printchar key, green;
}
printchar(ch, colour)
{
    setattr .foreground = colour;
    printf "%c", ch;
}