[REBOL] Re: Binding
From: otherchaz:mindspring at: 20-Nov-2002 6:23
> ; The following four lines when executead establish the
> ; word "greeting" into four different contexts.
>
> greeting: {Hi!}
> australia: context [ greeting: {G'day!} greet: does [greeting] ]
> france: context [ greeting: {Salut!} greet: does [greeting] ]
> sweden: context [ greeting: {Hey!} greet: does [greeting] ]
>
> ; instances-of-greeting will contain four values
> ; of type word! all of which have the same name {greeting}
> ; but which differ in that each is bound to a different context.
>
> instances-of-greeting: reduce [
> 'greeting
> in australia 'greeting
> in france 'greeting
> in sweden 'greeting
> ]
>
;so now we can pick random instances
;which all appear to be the same
h: func [][pick instances-of-greeting random 4]
i: h
j: h
k: h
l: h
;but they are randomly different
get i
get j
get k
get l
;for instance one possible outcome is
; >> get i
; == "Salut!"
; >> get j
; == "Hi!"
; >> get k
; == "Hey!"
; >> get l
; == "Salut!"
; run these functions of Ladislav Mecir
undefined?: func [
{determines, if a word is undefined}
word [any-word!]
] [
error? try [error? get/any :word]
]
s-c?: func [
{Are word1 and word2 bound to the same context?}
word1 [word!]
word2 [word!]
] [
found? any [
all [
undefined? word1
undefined? word2
]
all [
not undefined? word2
same? word1 bind use reduce [word1] reduce [
'first reduce [word1]
] word2
]
]
]
; define this block
languages: ["usa" "australia" "france" "sweden"]
;Why doesn't this return which language the greeting is in?
m: func [instance] [for index 1 4 1 [if s-c? [instance pick
instances-of-greeting index] pick languages index] ]
m i
C
