src/scss/bootstrap-4.0.0-alpha.6/scss/utilities/_float.scss

   1 @each $breakpoint in map-keys($grid-breakpoints) {
   2   @include media-breakpoint-up($breakpoint) {
   3     $infix: breakpoint-infix($breakpoint, $grid-breakpoints);
   4
   5     .float#{$infix}-left  { @include float-left; }
   6     .float#{$infix}-right { @include float-right; }
   7     .float#{$infix}-none  { @include float-none; }
   8   }
   9 }