Generated by SassMeister.com.

SassMeister-input.scss

// ----
// libsass (v3.2.5)
// ----

$o-grid-layouts: (A: 340px, X: 800px, Y: 1100px, Z: 1200px);
$_o-grid-layout-names: A, X, Y, Z;
$o-grid-gutters: (default: 10px);

@mixin oGridAddLayout($layout-name, $layout-width, $gutter-width: null) {
	$temp-layouts: ();
	$temp-gutters: ();

	// Add the new layout in the correct position:
	// (we want $o-grid-layouts and $o-grid-gutters to ordered from the smallest to the largest layout)
	@for $index from 1 through length($o-grid-layouts) {
		$previous-layout-width: if($index == 1, 0, map-get($o-grid-layouts, nth($_o-grid-layout-names, $index - 1)));
		$current-layout-name: nth($_o-grid-layout-names, $index);
		$current-layout-width: map-get($o-grid-layouts, $current-layout-name);

		$current-gutter-width: map-get($o-grid-gutters, $current-layout-name);

		@if not ($previous-layout-width > $layout-width or $current-layout-width < $layout-width) {
			$temp-layouts: map-merge($temp-layouts, ($layout-name: $layout-width));
			$temp-gutters: map-merge($temp-gutters, ($layout-name: $gutter-width));
		}

		$temp-layouts: map-merge($temp-layouts, ($current-layout-name: $current-layout-width));
		$temp-gutters: map-merge($temp-gutters, ($current-layout-name: $current-gutter-width));
	}
	$o-grid-layouts: $temp-layouts !global;
	$_o-grid-layout-names: map-keys($o-grid-layouts) !global;

	@if $gutter-width {
		$o-grid-gutters: map-merge($o-grid-gutters, $temp-gutters) !global;
	}

	$_o-grid-max-width: map-get($o-grid-layouts, nth($_o-grid-layout-names, -1)) !global;
}

@function oGridGutter($layout-name: 'default') {
	@if map-has-key($o-grid-gutters, $layout-name) {
		@return $layout-name + " key found in $o-grid-gutters. Has a value: " + (map-get($o-grid-gutters, $layout-name) != null);
	}

	$layout-index: index($_o-grid-layout-names, $layout-name);

	// The first layout (S) should get the default gutter
	@if $layout-index == 1 {
		@return oGridGutter();
	}

	$layout: nth($_o-grid-layout-names, $layout-index - 1);
	@return oGridGutter($layout);
}

@include oGridAddLayout($layout-name: B, $layout-width: 365px, $gutter-width: 30px);

/* $o-grid-gutters: #{inspect($o-grid-gutters)} */

test {
  content: "#{oGridGutter(B)}";
  /* WAT */
  content: "#{oGridGutter(A)}";
  content: "#{oGridGutter(Z)}";
}

SassMeister-output.css

/* $o-grid-gutters: (default: 10px, B: 30px) */
test {
  content: "B key found in $o-grid-gutters. Has a value: true";
  /* WAT */
  content: "A key found in $o-grid-gutters. Has a value: false";
  content: "Z key found in $o-grid-gutters. Has a value: false";
}