factor/library/collections/namespaces.factor

! Copyright (C) 2003, 2005 Slava Pestov.
! See http://factor.sf.net/license.txt for BSD license.
IN: namespaces
USING: hashtables kernel kernel-internals lists math sequences
strings vectors words ;

! Variables in Factor:
!
!   SYMBOL: x
!
!   5 x set
!   x get 2 + .
! 7
!   7 x set
!   x get 2 + .
! 9
!
! get ( name -- value ) and set ( value name -- ) search in
! the namespaces on the namespace stack, in top-down order.
!
! At the bottom of the namespace stack, is the global
! namespace; it is always present.
!
! bind ( namespace quot -- ) executes a quotation with a
! namespace pushed on the namespace stack.

: namestack ( -- ns ) 3 getenv ; inline

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

: namespace ( -- namespace )
    #! Push the current namespace.
    namestack car ; inline

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

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

: global ( -- g ) 4 getenv ;

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

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

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

: nest ( variable -- hash )
    #! If the variable is set in the current namespace, return
    #! its value, otherwise set its value to a new namespace.
    dup namespace hash [ ] [ >r {{ }} clone dup r> set ] ?ifte ;

: change ( var quot -- )
    #! Execute the quotation with the variable value on the
    #! stack. The set the variable to the return value of the
    #! quotation.
    >r dup get r> rot slip set ; inline

: on ( var -- ) t swap set ; inline

: off ( var -- ) f swap set ; inline

: inc ( var -- ) [ 1 + ] change ; inline

: dec ( var -- ) [ 1 - ] change ; inline

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

: make-hash ( quot -- hash ) {{ }} clone >n call n> ; inline

: with-scope ( quot -- ) make-hash drop ; inline

! Building sequences
SYMBOL: building

: make ( quot proto -- )
    #! Call , and % from "quot" to append to a sequence
    #! that has the same type as "proto".
    [
        dup thaw building set >r call building get r> like
    ] with-scope ; inline

: , ( obj -- )
    #! Add to the sequence being built with make-seq.
    building get push ;

: % ( seq -- )
    #! Append to the sequence being built with make-seq.
    building get swap nappend ;

! Building hashtables, and computing a transitive closure.
SYMBOL: hash-buffer

: closure, ( value key -- old )
    hash-buffer get [ hash swap ] 2keep set-hash ;

: (closure) ( key hash -- )
    tuck hash dup [
        hash-keys [
            dup dup closure, [ 2drop ] [ swap (closure) ] ifte
        ] each-with
    ] [
        2drop
    ] ifte ;

: closure ( key hash -- list )
    [
        {{ }} clone hash-buffer set
        (closure)
        hash-buffer get hash-keys
    ] with-scope ;