Name scoping mechanism

In large Forth programs, organizing namespace by breaking it up into different modules makes for a cleaner and less error prone system. The names of the four words used to do this are in common use by MPE.

This version can be added to any ANS Forth. It hides private words of a module in a temporary namespace. You are free to nest modules and manipulate the search order within a module, with the understanding that the implementation assumes the current wordlist is at the top of the search order.

: MODULE ( <name> -- )
   get-order wordlist dup set-current                 \ search order is:
   create dup , swap 1+   set-order ;                 \ ... public private

: END-MODULE
   previous definitions ;

: EXPORT ( <name> -- )
   get-order >in @ bl word find dup 0= abort" ???"    \ copy private
   >r >r >r 2 pick set-current r> >in ! : r> compile, \ to public
   postpone ; r> 0< 0= if immediate then
   over set-current set-order ;

: EXPOSE-MODULE ( <name> -- )                         \ add module to
   get-order ' >body @ swap 1+ set-order ;            \ search order

Usage

MODULE test
: bar boop over bop ;
: foo blah blivit ;
EXPORT foo
\ more...
END-MODULE

For debugging purposes, you can make the whole module visible with

EXPOSE-MODULE test.

Afterwards, you can hide it again using PREVIOUS.