This generates .m-t-10 or p-t-10 type helper classes.

_spacing_helpers.scss

/*
***UPDATED: modified as bootstrap 4 classes
This .scss loop will create "margin helpers" and "padding helpers" for use in your web projects.
It will generate several classes such as:
.mr-10 which gives margin-right 10 pixels.
.mr-15 gives MARGIN to the RIGHT 15 pixels.
.mt-15 gives MARGIN to the TOP 15 pixels and so on.
.pb-5 gives PADDING to the BOTTOM of 5 pixels
.pl-40 gives PADDING to the LEFT of 40 pixels
The first letter is "m" or "p" for MARGIN or PADDING
Second letter is "t", "b", "l", or "r" for TOP, BOTTOM, LEFT, or RIGHT
Third letter is the number of spacing in pixels. Adjust the amounts generated by editing the $spaceamounts variable below.
*/

$spaces: (5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 75, 100); // Change this to variate the pixel amount desired
$sides: (top, bottom, left, right); // Do not touch this variables

@each $space in $spaces {
  @each $side in $sides {
    .m#{str-slice($side, 0, 1)}-#{$space} {
      margin-#{$side}: #{$space}px !important;
    }
  
    .p#{str-slice($side, 0, 1)}-#{$space} {
      padding-#{$side}: #{$space}px !important;
    }
  }
}


/*
  RUN GULP to generate the classes. Now you can use these helpers to customize spacing on HTML elements.
*/