In all texts I've read, I've only seen the latter used. I can't clear things up really, just wanted to tell you that. I wouldn't be surprised if they meant the same thing and I wouldn't be surprised if they were very different. That's math for you
Usually, we can see the two used at the same time in this type of things :
can be written this way :
The is to define the domains, in which range does the domain "maps to"
The is to define by which value a number will be associated. "maps to" too.
All the time I've seen the two, was used for the domain/range and was used for associating a value to a number.
I don't know if you can see the difference with this example... ?