! :folding=indent:collapseFolds=1:

! $Id$
!
! Copyright (C) 2004 Slava Pestov.
! 
! Redistribution and use in source and binary forms, with or without
! modification, are permitted provided that the following conditions are met:
! 
! 1. Redistributions of source code must retain the above copyright notice,
!    this list of conditions and the following disclaimer.
! 
! 2. Redistributions in binary form must reproduce the above copyright notice,
!    this list of conditions and the following disclaimer in the documentation
!    and/or other materials provided with the distribution.
! 
! THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,
! INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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! PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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IN: namespaces
USE: combinators
USE: hashtables
USE: kernel
USE: lists
USE: math
USE: stack
USE: strings
USE: vectors

DEFER: namespace

: namestack ( -- ns ) 3 getenv ;
: set-namestack ( ns -- ) 3 setenv ;

: >n ( namespace -- n:namespace )
    #! Push a namespace on the namespace stack.
    namestack cons set-namestack ; inline

: n> ( n:namespace -- namespace )
    #! Pop the top of the namespace stack.
    namestack uncons set-namestack ; inline

: global ( -- g ) 4 getenv ;
: set-global ( g -- ) 4 setenv ;

: init-namespaces ( -- )
    global >n  global "global" set ;

: namespace-buckets 23 ;

: <namespace> ( -- n )
    #! Create a new namespace.
    namespace-buckets <hashtable> ;

: (get) ( var ns -- value )
    #! Internal word for searching the namestack.
    dup [
        2dup car hash* dup [
            nip nip cdr ( found )
        ] [
            drop cdr (get) ( keep looking )
        ] ifte
    ] [
        2drop f
    ] ifte ;

: get ( variable -- value )
    #! Push the value of a variable by searching the namestack
    #! from the top down.
    namestack (get) ;

: set ( value variable -- ) namespace set-hash ;
: put ( variable value -- ) swap set ;

: bind ( namespace quot -- )
    #! Execute a quotation with a namespace on the namestack.
    swap >n call n> drop ; inline