///Checks whether `$functions` exist in global scope.
///@access private
///@param {ArgList} $functions - list of functions to check for
///@return {Bool} Whether or not there are missing dependencies
 
@function sl-missing-dependencies($functions...) {
  $missing-dependencies: ();
  
  @each $function in $functions {
    @if not function-exists($function) {
      $missing-dependencies: append($missing-dependencies, $function, comma);
    }
  }
  
  @if length($missing-dependencies) > 0 {
    @warn "Unmet dependencies! The following functions are required: #{$missing-dependencies}.";
  }
  
  @return length($missing-dependencies) != 0;
}