What does the unary question mark (?) operator do?

Question

I saw this operator in HAML code. I wonder what it is for.

I see the following works:

> ?{
=> \"{\" 
> ?\\s
=> \" \" 
> ?a
=> \"a\"         


        

Answer 1

Re #2, a place I've found it useful is in conveying that a parameter I'm setting or value I'm testing for is intended to be a single character and not just that this happened to simply be a short string. It's a subtle readability/documentation thing, but worth considering for later maintainers (including myself).