What is this C++14 construct called which seems to chain lambdas?

Question

This is a follow-up question on this one: Lambda-Over-Lambda in C++14, where the answers explain the code.

It is about a lambda that creates another lambda which when ca

Answer 1

I looked around a bit and turns out the main functionality is reordering the function calls as explained in the answers to the original question.

So world(hello(stdout)); is rewritten to terminal(stdout)(hello)(world); which more generally could be written as compose(stdout)(hello)(world);.

• In Haskell this would written as world . hello $ stdout and is called function composition.
• In clojure it would be (-> stdout hello world) and is called the "thread-first" macro

I think it is only useful with decent partial application which lambdas provide a little bit, so we could have compose(4)([](int x){ return x + 7; })([](int x){ return x * 2; })([](int x){ return x == 22; }); which should return true if my calculation (and blind coding) is any good.

or to emphasize the partial application:

auto add7 = [](int x){ return x + 7; };
auto dbl = [](int x){ return x * 2; };
auto equal22 = [](int x){ return x == 22; };
assert(compose(4)(add7)(dbl)(equals22));

1 major issue with this implementation is probably that the result can't be evaluated because in the end a lambda is returned, so the construction in this answer might be better suited (function separated by comma instead of parenthesis).