memify-package {memify}

A Simple Framework to Construct and Maintain Functions That Keep State

Description

This package provides a simple way to construct and maintain versions of R functions that keep their state – i.e. "remember" their explicitly specifed arguments from previous calls. If not overridden, the remembered values of these arguments are automatically reused as the defaults for subsequent calls.

This may be convenient when a function with a large argument list – plotting functions are typical examples – needs to be repeatedly invoked with only a few changes in the arguments at each invocation; or when interacting with a function to determine what parameter values give the most informative results. While there are certainly other ways to do this, the simplicity of this approach may make it a useful alternative.

Details

The package has only one key function: memify(). It takes one argument, f, a function or a function name as a name/symbol or character string. The result, almost always assigned to a different name, is a new version of f that will keep state. It has S3 class "memified" that extends the function's original class vector . The original version of f of course remains.

Some minor additional convenience functions, arglist(), arglist(x) <- value, and an update method, update.memified(), are also provided. See the examples here and in their repective Help pages for usage.

Note

The arglist of a memified function consists only of arguments that were explicitly specified in a prior call. Hence, any formal default arguments that were not changed or specified will not be included in the memified function's arglist, which can be extracted via the arglist() function.

Author(s)

Bert Gunter

Maintainer: Bert Gunter <[e-mail]>

Examples

mod <- function(x, b = 5) x %% b
mod.m <- memify(mod) ## or memify("mod")
mod.m(7) ## using default b = 5
mod.m(b = 3) ## using remembered x = 7
mod.m()  ## the same as previous

arglist(mod.m) ## list of all memified arguments
update (mod.m, b = 9) ## silently updates arglist
arglist(mod.m)

arglist(mod.m) <- list(x=11) ## replaces the arglist with a new list
arglist(mod.m)
## b is no longer memified, so mod's default = 5 is used:
mod.m()

## cleanup
rm(mod.m)