I think this name is misleading, it's not really shorthand because it uses the same syntax. Best practice is to prefix the function name with a vendor prefix (in our case "-wikia"). This is from the Sass documentation: http://sass-lang.com/documentation/file.SASS_REFERENCE.html#function_directives

"It is recommended that you prefix your functions to avoid naming conflicts and so that readers of your stylesheets know they are not part of Sass or CSS. For example, if you work for ACME Corp, you might have named the function above -acme-grid-width."

So, it should be `-wikia-calc()`