Functional Sass

SassMeister-input.scss

// ----
// Sass (v3.3.4)
// Compass (v1.0.0.alpha.18)
// ----

@function _f-normalize($param){
  @if ( type-of($param) != list ) { $param : ($param,) };
  @return $param;
}

@function _f-check-func($func){
  @if not function-exisits($func) {
    @warn "#{$func} isn't a valid function";
    @return false;
  }
  @return true;
}
@function _f-check-funcList($func-list){
  @each $func in $func-list {
    @if not _f-check-func($func) {
      @return false;
    }
  }
  @return true;
}

// Filter all items in $value-list by calling the function $func for each item. 
// --------------------------------------------------------------------------------
// @param $value-list : List of values to map
// --------------------------------------------------------------------------------
// @throw "First parameter must be a list of values"
// --------------------------------------------------------------------------------
// @throw "Second parameter must be a list or string of functions"
// --------------------------------------------------------------------------------
// @return values | null
@function f-filter($value-list, $func){
  $value-list : _f-normalize($value-list);

  @if not _f-check-func($func){
    @return null;
  }
  
  $result: ();
  @each $value in $value-list{
    @if ( call($func, $value) ){
      $result : append($result, $value);
    }
  }
  @return $result;
}

// Run each value in $value-list through each function in $func-list
// --------------------------------------------------------------------------------
// @param $value-list : List of values to map
// --------------------------------------------------------------------------------
// @param $func-list : List of functions to run on the values
// --------------------------------------------------------------------------------
// @throw "First parameter must be a list of values"
// --------------------------------------------------------------------------------
// @throw "Second parameter must be a list or string of functions"
// --------------------------------------------------------------------------------
// @return values | null
@function f-map($value-list, $func-list){
  // Convert a single value to be in a list
  $value-list : _f-normalize($value-list);
  $func-list  : _f-normalize($func-list);
  
  @if not _f-check-func($func-list){
    @return null;
  }
  
  @each $func in $func-list{
    @for $i from 1 through length($value-list){
      $value-list : set-nth($value-list, $i, call($func, nth($value-list, $i)));
    }
  }
  @return $value-list; 
}


// Test functions 

@function add($x, $y){
  @return $x + $y;
}
@function mul($x, $y){
  @return $x * $y;
}
@function add2($x){
  @return add($x, 2);
}
@function mul2($x){
  @return mul($x, 2);
}
@function biggerThanFive($value){
  @return $value > 5;
}

$list : 1 2 3 4 5 6 7 8 9 10;

.test{
  map: f-map($list, add2);
  filter: f-filter($list, biggerThanFive);
  filterAndMap: f-map(f-filter($list, biggerThanFive), mul2);
  
}

SassMeister-output.css

.test {
  map: 3 4 5 6 7 8 9 10 11 12;
  filter: 6 7 8 9 10;
  filterAndMap: 12 14 16 18 20;
}