Primary dispatcher for functional programming

Description

UseFunction is an alternative approach to function dispatching vis-a-vis UseMethod. It is designed for people interested in writing functional programs in R as opposed to object-oriented programs.

Usage

UseFunction(fn.name, ...)

Arguments

Details

In most situations (i.e. following the conventions outlined by the futile.paradigm), explicit use of UseFunction is unnecessary as the system will automatically generate and execute this command as necessary. The only time it is necessary is when an abstract function has an ambiguous name (typically containing extraneous dots).

Explicit function definitions follow a simple template: fn.var <- function(...) UseFunction('fn.var', ...)

When calling the function, if no guards match, then an error is returned.

Value

Returns the value of the dispatched function

Note

For high-level API development, AbuseMethod may be more appropriate

Author(s)

Brian Lee Yung Rowe

See Also

AbuseMethod

Examples

# Note that these are trivial examples for pedagogical purposes. Due to their
# trivial nature, most of these examples can be implemented more concisely
# using built-in R features.

# Optional
#reciprocal <- function(...) UseFunction('reciprocal', ...)

reciprocal %when% is.numeric(x)
reciprocal %also% (x != 0)
reciprocal %must% (sign(result) == sign(x))
reciprocal %as% function(x) 1 / x

reciprocal %when% is.character(x)
reciprocal %as% function(x) reciprocal(as.numeric(x))

print(reciprocal)
reciprocal(4)

Results