Call a function: Difference between revisions

=={{header|R}}==

Translated from Python, when possible.

<lang rsplus>### Calling a function that requires no arguments

no_args <- function() NULL

no_args()

### Calling a function with a fixed number of arguments

fixed_args <- function(x, y) print(paste("x=", x, ", y=", y, sep=""))

fixed_args(1, 2) # x=1, y=2

fixed_args(y=2, x=1) # y=1, x=2

### Calling a function with optional arguments

opt_args <- function(x=1) x

opt_args() # x=1

opt_args(3.141) # x=3.141

### Calling a function with a variable number of arguments

var_args <- function(...) print(list(...))

var_args(1, 2, 3)

var_args(1, c(2,3))

var_args()

### Calling a function with named arguments

fixed_args(y=2, x=1) # x=1, y=2

### Using a function in statement context

if (TRUE) no_args()

### Using a function in first-class context within an expression

print(no_args)

### Obtaining the return value of a function

return_something <- function() 1

x <- return_something()

x

### Distinguishing built-in functions and user-defined functions

# Not easily possible. See

# http://cran.r-project.org/doc/manuals/R-ints.html#g_t_002eInternal-vs-_002ePrimitive

# for details.

### Distinguishing subroutines and functions

# No such distinction.

### Stating whether arguments are passed by value or by reference

# Pass by value.

### Is partial application possible and how

# Yes, see http://rosettacode.org/wiki/Partial_function_application#R</lang>