Suppose
(define data '((1 2) (2 3) (3 4)))
(println (map first data))
=>
(1,2,3)
Okydoky! That's what I expect. But,
(println (map 0 data))
=>
((1 2) (2 3) (3 4))
and
(println (map 1 data))
=>
((2) (3) (4))
Looks like (map
Shouldn't this be the other way around? That
(map 0 data) => (1 2 3)
(map 1 data) => (2 3 4)
Eddie[/i]
The
(0 '(1 2 3 4)) => (1 2 3 4)
(1 '(1 2 3 4)) => (2 3 4)
;; or
(1 2 '(1 2 3 4)) => (2 3)
and (map idx lst) behaves accordingly (the first part of the example)
what you mean is the
(set 'data '(1 2 3 4 5))
(data 0) => 1
(data 1) = 2
Lutz
ps: see http://newlisp.org/downloads/newlisp_manual.html#indexing
Yes,
I was wondering why doesn't map take implicit indexing instead of implicit slicing?
Would it not be more appropriate for map to take indexing? Why would we ever want map to be slicing?
Thanks!
Eddie
'map' always applies the first parameter to each element of the followoing list(s) parameter(s). You cannot suddenly change that sequence for the case of implicit indexing.
But you still could do:
(set 'data '(a b c d))
(map 'data '(3 2 1 0)) => (d c b a)
so everything works consistent. Note that data is quoted because 'map' evaluates the 1st parameter before applying it and so does implicit indexing.
mapping slice is useful for stripping all lists in a list of leading elements.
Lutz