R/ds_map_hashmap.R

In datastructures: Implementation of Core Data Structures

# datastructures: Implementation of core datastructures for R.
#
# Copyright (C) Simon Dirmeier
#
# This file is part of datastructures.
#
# datastructures is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# datastructures is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with datastructures. If not, see <http://www.gnu.org/licenses/>.


#' @include ds_map_unordered.R


#' @title Hashmap class
#'
#' @exportClass hashmap
#' @name hashmap-class
#' @rdname hashmap-class
#'
#' @description Implementation of a hashmap data structure, i.e. an unordered
#' collection of key-value pairs:
#' \deqn{f: keys -> values.}
#' Hashmaps only to store unique keys-value pairs. For a data structure
#' where multiple identical keys can be stores see \code{\link{multimap}}.
#' Inserting and accessing is amortized in \emph{O(1)}.
#' \code{hashmap} wraps a C++ \code{unordered_map} using Rcpp modules.
#' Also see \code{\linkS4class{bimap}} for mappings in both ways.
#'
#' @slot .map  \code{C++} object representing a mapping
#' @slot .key.class  the class of the keys
#'
#' @seealso  \code{\link{hashmap}} for creating a new \code{hashmap} object
#'
setClass("hashmap", contains = "unordered_map")


#' @title Create a new \code{hashmap}
#'
#' @export
#' @importFrom methods new
#'
#' @description Instantiates a new \code{\linkS4class{hashmap}} object,
#'  i.e. an unordered collection of key-value pairs with mapping
#'  \deqn{f: keys -> values}, where only unique key-value pairs
#'  can be stored.
#'
#' @param key.class  the primitive class type of the keys
#'
#' @return returns a new \code{hashmap} object
#'
#' @examples
#' # creates a hashmap<character, SEXP>
#' h <- hashmap()
#'
#' # creates a hashmap<integer, SEXP>
#' h <- hashmap("integer")
#'
#' # creates a hashmap<numeric, SEXP>
#' h <- hashmap("numeric")
hashmap <- function(key.class = c("character", "numeric", "integer")) {
  key.class <- match.arg(key.class)
  map <- switch(
    key.class,
    "character" = methods::new(hashmap_s),
    "numeric"   = methods::new(hashmap_d),
    "integer"   = methods::new(hashmap_i),
    stop("Error defining key class")
  )

  methods::new("hashmap",
    .key.class = key.class,
    .map = map
  )
}