## In R,
## Everything that **exists** is an object;
## Everything that **happens** is a function call :

## In the slides "Using R, Part 2 (2012)", we were looking at function f.maxi().
## I wrote on the BB:  
## The return value of a function is the value of the last evaluated function call
c
`<-`
`[`

## What *function* is  `[` ?
x <- 10:20
x[2]   # is exactly the same as
`[`(x, 2)

class(`[`)
class("[")
typeof(`[`)
typeof(ls)


## The difference between "[" and "[[" already shows with a simple named vector:
x <- 1:10
names(x)  <- LETTERS[1:10]
x
sum(x) # it is a vector
x["C"]
x[["C"]]

## Atomic objects:  numeric, character, logical,... vectors
## ---------------  and even matrices of those:
is.atomic(diag(4))

D  <- diag(4)
dim(D) <- NULL
D
D  <- diag(4); D # matrix ... but can also be treated as a vector:
D[7:9]
D[11]