URL validation without http:// or https:// in the URL Is is possible to use Craft's URL validation without http:// or https:// in the URL?
Or use some sort of function / filter to conditionally add it to the URL if it is missing?

I'm posting a form using sprout forms. The form contains a field that is set to validate as url.
If you post this field without adding http:// or https:// it doesn't validate.
Is it possible to somehow to set the defaultScheme of an url field to http without changing the core Craft UrlValidator or Yii's CUrlValidator?
To conditionally add http:// to strings that don't begin with http:// or https://, use the Twig matches operator in a comparison.

To keep the syntax compact, I use a ternary operator within the set tag. 

{# Set an example URL without `http://` #}
{% set url = 'example.com' %}

{# "Correct" the URL notation #}
{% set url = url matches '/^(https?:\\/\\/)/' ? url : 'http://' ~ url %}

{# Test output #}
{{ url }}


.

This is no full URL check in my regular expression, but you could simply work that in too. Pay attention to the escaping character \ that (currently) needs to be escaped itself, so you end up with \\ (it's wrong in the Twig docs).