Read or reread Chapter 5 of The Haskell Road, and make a list of questions on specific points that cause difficulty of understanding.
No questions
- The notation used in section 5.6 is confusing to me. Because I am used to read
|a|
as 'the size of a'. Am I correct when I say the collection of equivalence classes R:A/R = {|a| | a in A}
has the type set of sets? Implying that|a|
stands for the set of elements that are equivalent toa
in this case.
- In Lemma 5.81, if a set A would be empty then the proof for part 1 ( every equivalence-class is non-empty, because there is an element a in A, for which a is in the set A [reflexive] ) does not hold because there is no element a in A. Or do I have to see this differently?