SYS-SELF(2) SYS-SELF(2)
NAME
SELF - reference self as a compatible module type
SYNOPSIS
include "sys.m";
me := load Module SELF;
DESCRIPTION
An instance of a module of one type can acquire a reference
to itself as any compatible module type, using the Limbo
load operator with the special built-in module name $self.
Normally, applications use a synonym, the constant SELF,
which is defined by sys.m outside the declaration of the Sys
module (so that it need not be imported). Note that the
result of the load refers to the same instance that is cur-
rently executing (ie, the same module data).
This mechanism is most often used to obtain a reference to
the current module instance with a restriction of its module
type to a compatible subtype (eg, containing a subset of the
current module's declarations). For example, given modules
of the following types:
T: module
{
init: fn(nil: ref Draw->Context, nil: list of string);
special: fn(a, b: int);
};
S: module
{
special: fn(x, y: int);
};
G: module
{
init: fn(v: S);
};
an instance of module T can execute both the following:
t := load T SELF;
s := load S SELF;
but a module of type S could not load itself as type T.
The result might typically be assigned to a module variable
of that type (including passing as a parameter or storing in
an adt), as in:
g := load G "g.dis";
g->init(s);
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SYS-SELF(2) SYS-SELF(2)
See the definition and use of BufioFill in bufio(2) and
bufio-chanfill(2) for a practical example.
SEE ALSO
``The Limbo Programming Language'', Volume 2.
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