retList: Generic constructor function

In aoos: Another Object Orientation System

Description

This functions can be used to construct a list with class attribute and merged with another list called super. The constructed list will contain (by default) all visible objects from the environment from which retList is called.

Usage

retList(class = NULL, public = ls(envir), super = list(),
  superEnv = asEnv(super), mergeFun = envMerge, envir = parent.frame())

funNames(envir = parent.frame())

asEnv(x)

stripSelf(x)

Arguments

class	character giving the class name.
public	character with the names to include.
super	a list/object to be extended.
superEnv	environment where new methods will live in.
mergeFun	function with two arguments. Knows how to join/merge environments - mergeFun(envir, superEnv). Default: envMerge.
envir	this is the environment you want to convert into the list. Default is the environment from which the function is called.
x	a list

Details

funNames returns the names of functions in the environment from which it is called.

asEnv trys to find an environment for x. If x is NULL or an empty list, the function returns NULL. (Else) If x has an attribute called .self it is this attribute which is returned. (Else) If x is a list it is converted to an environment.

See Also

ls, +.Infix, print.Print

Examples

# To get a quick overview of the package:
vignette("Introduction", "aoos")

# To get more infos about retList:
vignette("retListClasses", "aoos")

# To get some infos about performance:
vignette("performance", "aoos")

# A simple class with one method:
Test <- function(.x) {
  getX <- function() .x
  retList("Test")
}

stopifnot(Test(2)$getX() == 2)

# A second example inheriting from Test
Test2 <- function(.y) {
  getX2 <- function() .x * 2
  retList("Test2", super = Test(.y))
}

stopifnot(Test2(2)$getX() == 2)
stopifnot(Test2(2)$getX2() == 4)

### Rational numbers example with infix operators and print method

Rational <- function(numer, denom) {

  gcd <- function(a, b) if(b == 0) a else Recall(b, a %% b)

  g <- gcd(numer, denom)
  numer <- numer / g
  denom <- denom / g

  print <- function(x, ...) cat(paste0(numer, "/", denom, "\n"))

  ".+" <- function(that) {
    Rational(numer = numer * that$denom + that$numer * denom,
             denom = denom * that$denom)
  }

  ".-" <- function(that) {
    if (missing(that)) {
      Rational(-numer, denom)
    } else {
      .self + (-that)
    }
  }

  # Return only what should be visible from this scope:
  retList(c("Rational", "Infix", "Print"),
          c("numer", "denom", "neg", "print"))

}

rational <- Rational(2, 3)
rational + rational
rational - rational

aoos documentation built on May 2, 2019, 3:47 p.m.