title: [DEFINED] name
description:
	precompiler-like test if a word is defined. The result
	is tested with => [IF]
discussion:
	[DEFINED] is part of the => ../../wordset/FPH
	also in FPH is [UNDEFINED]
	[DEFINED] and [UNDEFINED] are also in the OTA standard.
	There are quite a few words that do something similar
	but are named differently.

> Guido Draheim wrote:
>   gforth:  [IFDEF] and [IFUNDEF] in base system,
>            does the nesting with a dynamic parser vector ;
>             has neither [DEFINED] nor [NOT], but
>             has immediate DEFINED ( "name" -- 0|1 )
>   old pfe:  none in base system, strictly ansi
>   new pfe:  [DEFINED] and [NOT] in base system,
>             has also an independent C-like syntax that can not
>             mix with [IF] [ELSE] (#IFDEF .. #ELSE .. #ENDIF)
>   win32for: DEFINED and HAVE in base system, actually
>             DEFINED ( "name" -- str 0 | cfa flag ) non-immediate
>             HAVE ( "name" -- 0|flag ) non-immediate
>   bigforth: [IFDEF] and [IFUNDEF] in base system,
>             implemented just like gforth does ;
>             neither [DEFINED] nor [NOT] ;
>             has a non-immediate DEFINED?

possible-implementations:
: [DEFINED] ( IN: word -- CS: flag )
    BL WORD FIND NIP		\ incompatible with OTA
; IMMEDIATE
: [DEFINED] ( IN: word -- CS: flag )
    BL WORD FIND NIP 0<>	\ as in OTA
; IMMEDIATE
: [UNDEFINED] ( IN: word -- CS: flag )
    BL WORD FIND NIP 0=
; IMMEDIATE

( The difference between the two definitions of [DEFINED] is
in the value returned for IMMEDIATE words, 1 or -1.

--- $Id: index-v.txt,v 1.3 2002/05/21 19:17:54 mlg Exp $