rename the/2

[mndrix]

I've come to dislike how I named the/2. For one, it makes it sound like a variable has only one value. That's confusing in code like

the(integer, X),
member(X, [1,2,3,4]),

I wonder if var(X, Type) would be better. That looks a lot like a variable declaration. It also puts the type name after the variable, which matches the PlDoc format: X:type.

var(X, integer),
member(X, [1,2,3,4]),

There's still a little bit of confusion because var(X) fails if X is not a variable. However, var(X,Type) succeeds as long as X has the proper type.