Dynamic extend-only selectors

gistfile1.sass

@for $i from 0 through 6 {
  %row#{$i} {
    top: $block-size * $i;
  }
}

@each $year in 1997, 1994, 1993, 1991 {
  #y#{$year} a {
    @extend %row3;
  }
}

With $block-size set to 118px, it compiles to:

#y1997 a, #y1994 a, #y1993 a, #y1991 a {
  top: 354px;
}