Data commit

Task/Call-a-function/R/call-a-function.r

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+### 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