function( arglist ) expr return(value)
args and body for accessing the arguments
and body of a function.
debug for debugging; invisible for
return(.)ing invisibly.
norm <- function(x) sqrt(x%*%x)
norm(1:4)
## An anonymous function:
(function(x,y){ z <- x^2 + y^2; x+y+z })(0:7, 1)