How to exclude some keywords from a search with Search API?
I believe the "custom_search" module can do that. http://drupal.org/project/custom_search

Although I don't know whether the exact boolean syntax is used, I know the module offers two ways to search in the way you want:


With three different text fields (one for OR, one for AND, and one
for WITHOUT)
With one text field (By using some kind of syntax like
you described)