I’m a little confused on where you are getting your information. For one instance, I was confused on what a pure predicate was, until I used my background knowledge from lambda calculus to figure out that it means that it is fully self-contained, meaning that things like P(x) = -x work, but not P(x) = x^y (an alias of this in the calculus is a “combinator”). However, I am still confused on what a pure variable is. Is it a variable contained in a pure predicate? Please tell me where you get the sources, or, at the very least, a compilation of them with your background knowledge. Speaking of which, I have found this somewhat useful link.
I’m a little confused on where you are getting your information. For one instance, I was confused on what a pure predicate was, until I used my background knowledge from lambda calculus to figure out that it means that it is fully self-contained, meaning that things like P(x) = -x work, but not P(x) = x^y (an alias of this in the calculus is a “combinator”). However, I am still confused on what a pure variable is. Is it a variable contained in a pure predicate? Please tell me where you get the sources, or, at the very least, a compilation of them with your background knowledge. Speaking of which, I have found this somewhat useful link.