but {operators}

Modification of function arguments

Description

Modifies the arguments of a function

Usage

  fun %but% x

Arguments

fun

Function to modify

x

Modifier

Value

A function with the same body as the fun argument but with a different list of arguments.

Note

The %but% operator is S3-generic with the following methods:

- A default method which does nothing more than returning the fun function.

- A charactor method. In that case, x describes the logical arguments of the function. x is a single character string containing one or several token of the form ab where b is the first letter of the logical argument we wish to modify and a is an optional modifier. a can be empty or +, in which case the argument will be set to TRUE; - in which case the argument will be set to FALSE; or ! in which case the argument will be the opposite of the current value in fun

- A list. In that case, arguments that are part of the formal arguments of fun and elements of the list x are updated to the element in x

Author(s)

Romain Francois <[e-mail]>

See Also

args, formals

Examples

        
### default method, nothing is done
rnorm %but% 44

### character method, operating on logical arguments
grep %but% "pf"     # grep, with perl and fixed set to TRUE
grep %but% "i-e"    # grep, ignoring the case but not using extended regular expressions
( grep %but% "vp" )( "blue", colors() )

### list method 
rnorm %but% list( mean = 3 )
rnorm %but% list( nonsense = 4 )