Generated by SassMeister.com.

SassMeister-input.scss

// ----
// libsass (v3.1.0)
// ----

// S/Small
$s: (null null);

// M/Medium
$m: (800px 900px);

// L/Large
$l: (1000px null);

@mixin flextype($type_styles...){
  @each $type_style in $type_styles {
    
    test: $type_style;
    
    @each $mq_min, $mq_max, $font_size, $line_height, $letter_spacing in $type_style{
      font-size: $font_size;
      line-height: $line_height;
      letter-spacing: $letter_spacing;
    }
  }
}

@include flextype($s 1.2rem 1.5 -1px, $m 1.4rem 1.5 -1px, $l 1.8rem 1.5 -1px);

SassMeister-output.css

test:  1.2rem 1.5 -1px;
test: 800px 900px 1.4rem 1.5 -1px;
test: 1000px 1.8rem 1.5 -1px;