tests/testthat/987654321_stat102a_test.R

In oonyambu/stats_102A: Grade stats 102A (UCLA)

gcd <- function(a, b) {
  stopifnot(a > 0, b > 0, as.integer(a) == a, as.integer(b) == b)
  while (b - a) if (a > b) a <- a - b else b <- b - a
  a
}

gcd_3 <- function(x, y, z) gcd(gcd(x, y), z)

get_factors <- function(x) {
  stopifnot(x > 0, as.integer(x) == x)
  n <- c()
  i <- 2
  while (x > 1) {
    if (!x %% i) {
      n <- c(n, i)
      x <- x / i
      i <- i - 1
    }
    i <- i + 1
  }
  n
}

is_prime <- Vectorize(
  function(x) {
    if (as.integer(x) != x) {
      FALSE
    } else if (x <= 3) {
      x > 1
    } else {
      !any(!x %% 2:floor(sqrt(x)))
    }
  }
)