## How can a variadic template be used to generate a left-associative expression (aka left fold) in c++11?

I would like to use a c++ template to aggregate (fold) multiple arguments using a binary operation. Such a template could be used as follows:

## Fold expression with comma operator and variadic template parameter pack

Based on c++ operator doc, ',' is a left to right operator. It is meaning a, b, c, d meaning (((a, b), c),d) not (a, (b, (c, d))). This is important if a, b, c, d are statements.

## Can my implementation of filter be improved?

An exercise in Haskell from First Principles says to implement filter using foldr and this is what I came up with but it feels and looks clunky. Is there a more natural way to implement it with a foldr?

## Understanding Folds in Haskell

From what I understand about folds in Haskell, foldl (-) 0 [1..5] gives a result of -15 by calculating 0-1-2-3-4-5, and foldr (-) 0 [1..5] gives a result of -5 by calculating 5-4-3-2-1-0. Why is it then that both foldl (++) "" ["a", "b", "c"] and foldr (++) "" ["a",...

## How to break out from a fold function in haskell when the accumulator met a certain condition?

I'm calculating the sum of a list after applying someFunction to every element of it like so:someFunction is very resource heavy so to optimise it I want to stop calculating the sum if it goes above a certain threshold.