The Importance of $g

$g is the logical name for #349, the Game Utilities object, which is a child of the Generic Utilities Package(#79).

$g is the standard place for storing utilities relevant to a particular virtual environment, but that are not part of the standard distribution of utilities that come preloaded into the LambdaCore database (e.g. $string_utils, $list_utils, $command_utils, $object_utils, $time_utils, etc.). In general, though, only wizards will create utilities and save them on $g.

As an example, the accessor functions

$g:update_event(player, this) and
$g:update_award(player, this)

are verbs defined on $g and owned by the wizard.

The Iron Rule: No Object Numbers in Code

More importantly, $g also provides a good way for programmers to create and use symbolic names (and avoid object numbers in code).

Using $g to create and store symbolic names is good programming practice.
Using object numbers in code is a VERY BAD idea (and it will cost you points)

The most common way for programmers to use this utilities package is to define a property on $g, and assign it a frequently used object.

For example, if you were creating a member function machine (object #1722, say) for demonstrating how the member function operates, and you will need to refer to the Member Function Room's (#1717) contents in your code, you could write

#1717.contents <== object number in code: BAD

but a far better method would be to add a member_function_room property to the Game Utilities(#349) object, $g, and then reference the contents of your function room like so:

$g.member_function_room.contents

This works because

$g references object #349
$g.member_function_room references object #1717, and
$g.member_function_room.contents returns a list

How to Add Properties to $g

If you owned $g you could add properties like this

@property $g.member_function_room #1717

But the wizard owns $g, so you must use the accessor function, like so:

;$g:add_dollarg_prop("member_function_room", #1717)

$g Properties That Already Exist

The following are already defined on $g. You demo machine is probably on this list. If not, use add_dollarg_prop to add it.

    Member_Machine: #1722
    symbolp_machine: #1737
    get_machine: #1741
    null_machine: #1758
    PLUSP_machine: #1778
    car_cdr_machine: #1784
    Concatenate_Machine: #1791
    plus_or_minus_1: #1792
    max_and_min_machine: #1801
    remprop_machine: #1814
    sublis_machine: #1750
    Comparison_on_Numbers_Machine: #1829
    Subseq_Function_Machine: #1854
    equal_machine: #1887
    plus_and_minus_operation_machine: #1890
    inc_and_dec_machine: #1907
    cons_machine: #1923
    machine_box: #1925
    MINUSP_machine: #1893
    gensym_machine: #1958
    Abs_machine: #1965
    Random_Machine: #1968
    listp_machine: #1970
    dolist_machine: #1918
    char_equal_machine: #2003
    nth_machine: #1763
    Cadr/Cdar_machine: #1862
    floor_machine: #1839
    mod_machine: #2046
    butlast_machine: #2048
    exp_expt_machine: #1805
    LIST_function_machine: #2050
    Length_Machine: #2051
    sqrt_machine: #2052
    arithmetic_machine: #2056
    alphanumericp_machine: #2067
    intersection_machine: #2077
    union_machine: #2078
    Trigonometric_Functions_Machine: #1754
    float_machine: #2006
    Association_Function_Machine: #1728
    count_machine: #1730
    Position_Machine: #2071
    merge_machine: #1892
    reverse_machine: #2062
    eq_and_eql_machine: #1819
    equal_and_equalp_machine: #1887
    member_function_room: #1717