R is GNU S, not C.... [was "how to get or store ....."]

From: vincent at 7d4.com

ronggui a écrit :

I think it is NOT just for historical reason.
see the following example:

rm(x)
mean(x=1:10)

[1] 5.5

x

Error: object "x" not found

x is an argument local to mean(),
did you expect another answer ?

mean(x<-1:10)

[1] 5.5

x

 [1]  1  2  3  4  5  6  7  8  9 10

What is the goal of this "example" ?

I believe it's to show why "<-" is to be preferred over "=" for
assignment...

Here with "<-",
(voluntary, or not, side effect)
the global variable x is, also, created.
Did the writer really want that ???

Very much so, I believe.

I though there were other specific statements
especially intended for global assignment, eg "<<-".

You need to distinguish assignment in function _call_ and assignment in
function _definition_.  They ain't the same.

If this example was intended to prove "<-"
is better than "="
... I'm not really convinced !

In that case, let's try another one (which is one big reason I stopped using
"=" for assignment):

long.comp <- function(n) {

+     Sys.sleep(n)
+     n
+ }

result = long.comp(30)
system.time(result = long.comp(30))

Error in system.time(result = long.comp(30)) : 
unused argument(s) (result ...)

system.time(result <- long.comp(30))

[1]  0.00  0.00 30.05    NA    NA

str(result)

num 30

Cheers,
Andy