Keeping function names when stored in an object

Question

I am preparing a package where users have to store functions and their associated arguments in a list for later use. This is a typical example of how it works:<

Answer 1

You could use alists:

parameters <- list(a1 = alist(fun = dnorm,
                             args = list(mean = 150, sd = 100)),
                   a2 = alist(fun = dpois,
                             args = list(lambda = 40)))
#probably better to write a constructor method for parameters objects


x <- 1:100
myfunction <- function(x, var, parameters)
{ f <- function(x) do.call(fun, c(list(x), args))
  formals(f) <- c(formals(f), parameters[[var]]) 
  results <- list(var = var,
                  y = f(x),
                  parameters = parameters)
  class(results) <- "customclass"
  return(results)
}

print.customclass <- function(X)
{
  cat("Function name:", X$parameters[[X$var]]$fun)
}

myfunction(x, "a1", parameters)
#Function name: dnorm

Answer 2

I'd suggest to define your parameters argument with the function name, instead of the function itself and retrieve the function in the body of myfunction through match.fun:

    parameters <- list(a1 = list(fun = "dnorm",
                         args = list(mean = 150, sd = 100)),
               a2 = list(fun = "dpois",
                         args = list(lambda = 40)))

    myfunction <- function(x, var, parameters)
    {
        results <- list(var = var,
                y = do.call(match.fun(parameters[[var]]$fun), 
                            c(list(x), parameters[[var]]$args)),
                parameters = parameters)
        class(results) <- "customclass"
        return(results)
    }