=-------------------------------------------------
=section assignment vs binding
=-------------------------------------------------
* A = B ;
"assign" means :
evaluate the *value* on the right hand side and
*distribute* it ( value ) among the containers ( which if
needed should be created/changed ) on the left .
* A := B ;
*alias* or *bind* variable containers to names :
take a hold of containers on the right hand side and
*distribute* them (containers ) among ( bind them to )
*names* on the left.
there is a special binding operator ::= that is same as := but force
binding to happen at compile time .
so , again ,
* after the assignment ( variables at ) left and right hand sides
refer to the same values through different ( independent )
containers. ( modulo some Copy on Write magic ) .
$a = $b ;
($a, $b) = ($b, $a);
(@a, @b) = (@b, @a);
@a = ( @b, @c ) ;
&a = sub { ... } ;
* after the binding -- ( names, if there were names ! ) at right hand
side and names ( which surely have to be there ! ) at left hand
sides refer to the same containers.
$a := $b ;
($a, $b) := ($b, $a);
(@a, @b) := (@b, @a);
@a := ( @b, @c ) ;
&a := sub { ... } ; #same as sub a { ... }
#here @a *interface* can change values seen by $x, $y, $z, @c
@a := ( $x , $y, $z , @c) ;
#here first *anonymous container is created holding (1, 2, 3) and then
#this container is bound to name '@a'
@b := ( 1 ,2 ,3 ) ;
as a consequence, run-time properties are "passed" ( from the variable
on the right side to variables on the left ) in both cases , since
they are attached to values . compile-time properties are "passed"
only at binding since they are attached to containers .
