On Sat, Oct 24, 2015 at 8:12 PM, Janis Voigtländer < janis.voigtlaender@gmail.com> wrote:
It has already been established in this thread what Charles meant by 3.
He meant that a fold-function that has the property he is after would guarantee that it:
a) takes all the content elements from a data structure, say x1,...,xn,
b) builds an application tree with the to-be-folded, binary operation f in the internal nodes of a binary tree, whose leafs, read from left to right, form exactly the sequence x1,...,xn,
c) evaluates that application tree.
Do you agree that what I describe above is a property of a given fold-like function, not of the f handed to that fold-like function?
I might lack some basic knowledge, so thanks for asking. What does it mean to take all the content elements from a data structure? If one has f a = Bool -> a, and a value xs :: f Int xs True = 2 xs False = 3 what are x1 and x2? Best, Matteo PS. I won't be able to read the answer before tomorrow. :-)