Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.4.9)
// Compass (v1.0.1)
// SassyLists (v2.2.1)
// ----

// function fibonacci(){
//   var fn1 = 1;
//   var fn2 = 1;
//   while (1){
//     var current = fn2;
//     fn2 = fn1;
//     fn1 = fn1 + current;
//     var reset = yield current;
//     if (reset){
//         fn1 = 1;
//         fn2 = 1;
//     }
//   }
// }

@import "SassyLists";

$__static__: ();
$__generators__: ();
$__current__: false;

// These are just helpers.
@function pop($list) {
    @return sl-remove-nth($list, 1);
}

@function get($map, $properties) {
    $map: map-get($map, nth($properties, 1));
    $properties: pop($properties);

    @if not $map {
        @return null;
    }

    @if length($properties) == 0 {
        @return $map;
    }

    @return get($map, $properties);
}

@function set($map, $properties, $value) {
    $property: nth($properties, 1);
    $properties: pop($properties);
    $child-map: map-get($map, $property);
    
    @if not $child-map {
      $child-map: ();
    }

    @if length($properties) == 0 {
        @return map-merge($map, ($property: $value));
    }

    @return map-merge($map, ($property: set($child-map, $properties, $value)));
}

@function static($key, $value, $set: false) {
  // Define static variables only if the variable doesn't exist
  // OR if $set is true (as an override)
  @if not map-has-key($__static__, $key) or $set {
    $__static__: set($__static__, $key, $value) !global;
  }
  
  @return get($__static__, $key);
}
@function get-static($key) {
  @return get($__static__, $key);
}

@function set-static($key, $value) {
  @return static($key, $value, true);
}

@function gen-while($condition) {
  $generator: get-generator();
  $__generators__: set($__generators__, $__current__ loop-condition, $condition) !global;
  
  @if $condition and get($generator, traversal) == get($generator, state) {
    $__generators__: set($__generators__, $__current__ loop, get($generator, state)) !global;
    
    @return true;
  } @else {
    $__generators__: set($__generators__, $__current__ loop, false) !global;
    
    @return false;
  }
}

@function gen-endwhile() {
  $generator: get-generator();
  $condition: get($generator, loop-condition);
  
  @if $condition and get($generator, traversal) == get($generator, state) {
    $__generators__: set($__generators__, $__current__ state, get($generator, loop)) !global;
  }
  
  @return true;
}

@function set-generator($name) {
  $generator: (
    state: 0,
    traversal: 0,
    loop: false,
    done: false
  );

  @if not map-has-key($__generators__, $name) {
    $__generators__: set($__generators__, $name, $generator) !global;
  }
  
  $__generators__: set($__generators__, $name traversal, 0) !global;
 
  $__current__: $name !global;
  
  @return $generator;
}

@function get-generator($name: $__current__) {
  @return get($__generators__, $name);
}

@function yield($value) {
  $generator: get-generator();
  
  // Do not yield specified value until traversal and state are equal
  $yield-value: get($generator, value);
  
  @if get($generator, traversal) == get($generator, state) {
    $__generators__: set($__generators__, $__current__ value, $value) !global;
    
    $yield-value: $value;
  } 
  
  $__generators__: set(
    $__generators__,
    $__current__ traversal,
    get($generator, traversal) + 1) !global;
  
  @return $yield-value;
}

@function generate-next($name: $__current__) {
  $iterate-generator: call($name);
  $generator: get-generator($name);
  $yield-value: get($generator, value);
  
  @if not get($generator, loop) {
    $__generators__: set(
      $__generators__,
      $__current__ state,
      get($generator, state) + 1) !global;
  }
  
  @return $yield-value;
}

// =================================
// Here's the (almost) desired code:
// =================================
@function fibonacci() {
  $generator: set-generator('fibonacci');
  
  $yield: yield('Ready...');
  $yield: yield('Set...');
  $yield: yield('Go!');
  
  $fib1: static('fib1', 1);
  $fib2: static('fib2', 1);
  
  // Pretend that this looks normal.
  $while: gen-while(true);  
    $current: get-static('fib2');
    $fib2: set-static('fib2', get-static('fib1'));
    $fib1: set-static('fib1', get-static('fib1') + $current);
    $yield: yield($current);
  $while: gen-endwhile();
  
  @return $yield;
}

.fibonacci {
  content: generate-next(fibonacci);
  content: inspect($__generators__);
  content: generate-next(fibonacci);
  content: inspect($__generators__);
  content: generate-next(fibonacci);
  content: inspect($__generators__);
  content: generate-next(fibonacci);
  content: inspect($__generators__);
  content: generate-next(fibonacci);
  content: inspect($__generators__);
  content: generate-next(fibonacci);
  content: inspect($__generators__);
  content: generate-next(fibonacci);
  content: inspect($__generators__);
  content: generate-next(fibonacci);
  content: inspect($__generators__);
  content: generate-next(fibonacci);
  content: inspect($__generators__);
  content: generate-next(fibonacci);
  content: inspect($__generators__);
  content: generate-next(fibonacci);
  content: inspect($__generators__);
  content: generate-next(fibonacci);
  content: inspect($__generators__);
}

SassMeister-output.css

.fibonacci {
  content: "Ready...";
  content: ("fibonacci": ((state: 1, traversal: 4, loop: false, done: false, value: "Ready...", loop-condition: true)));
  content: "Set...";
  content: ("fibonacci": ((state: 2, traversal: 4, loop: false, done: false, value: "Set...", loop-condition: true)));
  content: "Go!";
  content: ("fibonacci": ((state: 3, traversal: 4, loop: false, done: false, value: "Go!", loop-condition: true)));
  content: 3;
  content: ("fibonacci": ((state: 3, traversal: 4, loop: 3, done: false, value: 3, loop-condition: true)));
  content: 5;
  content: ("fibonacci": ((state: 3, traversal: 4, loop: 3, done: false, value: 5, loop-condition: true)));
  content: 8;
  content: ("fibonacci": ((state: 3, traversal: 4, loop: 3, done: false, value: 8, loop-condition: true)));
  content: 13;
  content: ("fibonacci": ((state: 3, traversal: 4, loop: 3, done: false, value: 13, loop-condition: true)));
  content: 21;
  content: ("fibonacci": ((state: 3, traversal: 4, loop: 3, done: false, value: 21, loop-condition: true)));
  content: 34;
  content: ("fibonacci": ((state: 3, traversal: 4, loop: 3, done: false, value: 34, loop-condition: true)));
  content: 55;
  content: ("fibonacci": ((state: 3, traversal: 4, loop: 3, done: false, value: 55, loop-condition: true)));
  content: 89;
  content: ("fibonacci": ((state: 3, traversal: 4, loop: 3, done: false, value: 89, loop-condition: true)));
  content: 144;
  content: ("fibonacci": ((state: 3, traversal: 4, loop: 3, done: false, value: 144, loop-condition: true)));
}