R/isPrime.R

Defines functions isPrime

## Copyright (c) 2016, James P. Howard, II <jh@jameshoward.us>
##
## Redistribution and use in source and binary forms, with or without
## modification, are permitted provided that the following conditions are
## met:
##
##     Redistributions of source code must retain the above copyright
##     notice, this list of conditions and the following disclaimer.
##
##     Redistributions in binary form must reproduce the above copyright
##     notice, this list of conditions and the following disclaimer in
##     the documentation and/or other materials provided with the
##     distribution.
##
## THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
## "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
## LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
## A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
## HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
## SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
## LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
## DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
## THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
## (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
## OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#' @title Test for Primality
#'
#' @description
#' Test the number given for primality.
#'
#' @param n n
#'
#' @details
#' This function tests \code{n} if it is prime through repeated division
#' attempts.  If a match is found, by finding a remainder of 0,
#' \code{FALSE} is returned.
#'
#' @return boolean TRUE if \code{n} is prime, FALSE if not
#'
#' @family algebra
#'
#' @examples
#' isPrime(37)
#' isPrime(89)
#' isPrime(100)
#'
#' @export
isPrime <- function(n) {
    if(n == 2)
        return(TRUE)

    for(i in 2:sqrt(n))
        if(n %% i == 0)
            return(FALSE)

    return(TRUE)
}
howardjp/cmna documentation built on Sept. 28, 2021, 7:22 p.m.