Sass, testing for empty values.

SassMeister-input.scss

// ----
// Sass (v3.3.5)
// Compass (v1.0.0.alpha.18)
// ----

// testing for empty values
// In Sass "", 0, () evaluate to true...

@function empty($value) {
  @if not $value 
      or $value == "" 
      or $value == 0
      or $value == ()
      or length($value) == 0 {
    @return true;
  }
  @return false;
}

// Test
sass {
  /* 
   empty() 
  */
  @each $test in false, null, "", 0, (), ("",), ("": "") {
    #{inspect($test)}: empty($test);
  }
  /* 
   core
  */
  test: "" == false;
  test: 0 == false;
  test: () == false;
}

SassMeister-output.css

sass {
  /* 
   empty() 
  */
  false: true;
  null: true;
  "": true;
  0: true;
  (): true;
  ("",): false;
  ("": ""): false;
  /* 
   core
  */
  test: false;
  test: false;
  test: false;
}