[REBOL] Re: Correct Behaviour? Was False = 2 ????
From: lmecir:mbox:vol:cz at: 5-Jul-2001 11:02
Hi,
1) there is no need to change AT to 0-based, because we have got SKIP
2)
based?: func [
f [any-function!]
block [block!]
i [integer!]
] [
(index? block) + i - (index? f block i)
]
a: skip [-1 0 1 2] 2 ; == [1 2]
based? :at a 1 ; == 1
based? :at a 2 ; == 1
based? :skip a 0 ; == 0
based? :skip a 1 ; == 0
based? :at a 0 ; == 0
based? :at a -1 ; == 0
based? :at a -2 ; == 0
based? :skip a 0 ; == 0
based? :skip a -1 ; == 0
==> AT is implemented inconsistently, because it is neither
1-based, nor 0-based!
3) if I look at the functions: FIRST, SECOND, ..., I found their behaviour
natural
4) PICK looks OK as a generalization of the FIRST, SECOND, ... for 1<= index
<= length? block
5) PICK is neither 1-based, nor 0-based (It is worse than AT, because it's
got an "Emental Property" - see a "hole" at zero!). ==> Inconsistent.
6) PICK is "Too Consistent" for me in this case:
pick [none] 1 ; == none
pick [none] 2 ; == none
7) the following behaviour is inconsistent from the zero-based POV as well
as from one-based POV:
a: [1]
remove a
b: skip a 1
index? b ; == 1
while:
a: [1]
b: skip a 1
remove a
index? b
** Script Error: Out of range or past end
** Where: halt-view
** Near: index? b
There are two ways how to get a different behaviour here:
7a) define:
skipped?: func [
block [block!]
] [
if error? try [return (index? block) - 1] [
(index? tail block) - 1
]
]
a: [1]
b: skip a 1
remove a
skipped? b ; == 0
7b) define a JUMP and JUMPED? functions having this property:
a: [1]
b: jump a 1 ; == []
jumped? b ; == 1
remove a
jumped? b ; == 1
a: [1]
remove a
b: jump a 1
jumped? b ; == 1
This would have a capability of allowing any-base indexing, my Rebol
Brothers.
Howgh
