Structs

Structs are a way to group related variables or lists together.

Declaration

struct my_struct {
    x,
    y,
    z
}

Default values

Struct fields can have default values.

struct my_struct {
    field = "default_value"
}

my_struct v = my_struct {};
# -> v.field == "default_value"

Usage

Declaring a struct variable

my_struct my_variable = value;

Declaring a struct list

list my_struct my_list;

Accessing struct fields

Accessing a struct variable field

my_variable.my_field

Accessing a struct argument field

$my_argument.my_field

Accessing a struct list field

my_list[index].my_field

Struct literals

Struct literals are a way to create structs.

my_struct my_variable = my_struct {
    x: 10,
    y: 20,
    z: 30
};

Passing structs

You can pass structs to procedures via arguments or variables.

list my_struct my_list;

proc my_procedure my_struct arg {
    # code
}

onflag {
    my_procedure my_struct {
        x: 10,
        y: 20,
        z: 30
    };
    my_procedure my_list[1];
}

onflag {
    my_struct foo = my_struct {
        x: 10,
        y: 20,
        z: 30
    };
    my_struct bar = foo;
}

Limitations

Variables

During struct variable assignment, fields are assigned sequentially. Consequently, if a field references another field of the same struct during assignment, it will use the updated value of previously assigned fields rather than their original values.

For example:

pair = Pair { left: 100, right: 200 };
pair = Pair { left: pair.left + 100, right: pair.left };
# Result: pair = Pair { left: 200, right: 200 };

In this case, the pair.left field is assigned first with the value 200, and subsequently pair.right references the updated value of pair.left.

This behavior can be mitigated by reordering the fields in the struct literal:

pair = Pair { right: pair.left, left: pair.left + 100 };

Same issues apply to all augmented assignment operators (+=)

Lists

The issue with order of assignment applies to struct lists as well.