Prime number in Sass.

SassMeister-input.scss

// ----
// Sass (v3.3.9)
// Compass (v1.0.0.alpha.20)
// ----

// Prime number
// https://en.wikipedia.org/wiki/Prime_number


// Returns whether `$n` is a prime number.
// ---
// @param {number} $n
// ---
// @return {bool}

@function is-prime($n) {
  @if type-of($n) != number {
    @warn "#{$n} is not a number for `is-prime`.";
    @return null;
  }
  
  @if $n < 2 or $n != floor($n) {
    @return false;
  }
  
  @if $n % 2 == 0 { @return $n == 2; }
  @if $n % 3 == 0 { @return $n == 3; }

  $i: 5;
  $m: ceil(sqrt($n));
  @while $i <= $m {
    @if $n % $i == 0 or $n % ($i + 2) == 0 {
      @return false;
    }
    $i: $i + 6;
  }
 
  @return true;
}


// Returns the factorial of a non-negative integer.
// ---
// @param {number} $n: a non-negative integer
// ---
// @return {number}

@function fact($n) {
  @if $n < 0 or  $n != floor($n) {
    @warn "#{$n} is not a positive integer for `fact`.";
    @return null;
  }
  
  $ret: 1;
  @while $n > 0 {
    $ret: $ret * $n;
    $n: $n - 1;
  }
  
  @return $ret;
}


// Returns whether `$n` is a prime number.
// ---
// @param {number} $n
// ---
// @return {bool}

@function _is-prime($n) {
  @if type-of($n) != number {
    @warn "#{$n} is not a number for `is-prime`.";
    @return null;
  }
  
  @if $n < 2 or $n != floor($n) {
    @return false;
  }
  
  @return fact($n - 1) % $n == $n - 1;
}

// Tests
is-prime {
  $fixture: (
    7: true,
    10: false,
    37: true,
    60: false,
    373: true,
    390: false,
    1427: true,
    1683: false,
    7879: true,
    7881: false,
    // 2011: true,
    // 9007199254740881: true
  );
  
  $tests: '';
  @each $num, $bool in $fixture {
    $pass: is-prime($num) == $bool;
    $tests: $tests + if($pass, '✔ ', 'X ');
  }
  is-prime: $tests;
  
   $tests: '';
  @each $num, $bool in $fixture {
    $pass: _is-prime($num) == $bool;
    $tests: $tests + if($pass, '✔ ', 'X ');
  }
  _is-prime: $tests;
}

SassMeister-output.css

@charset "UTF-8";
is-prime {
  is-prime: "✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ";
  _is-prime: "✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ✔ ";
}