parameter blocks

1.20: adda/dstr/param'blocks:

. back when I was studying inside mac
-- before mac os X --
they had param'blocks:
huge records that would hold lots of options
so that when using services like window mgt
you didn't have long param' lists with every call .

. it would be even more convenient if
merely importing a subprogram would also
declare and implicitly apply a param'block for you .
. the translated code would have to include
a parameter -- the pointer to the param'block --
but user's code would not have to include that .

. param'blocks can be viewed as
caller-defined defaults
-- that's in contrast to the usual
subprogram-defined defaults
where if you don't specify an arg'
then the sub' provides one for you .

. param'blocks could also work like packages
in that name clashes could be avoided by
using the sub's name as owner of the global:
sub`global .

. another way to do this is ada`packaging:
have the sub' be a component of it's struct
where you can have
sub`[caller-defined default]`= [your pref's],
and then also do a call that uses that preference:
sub`fun(args) .