thread-first

thread-first is a Lisp macro in `subr-x.el'.

(thread-first &rest FORMS)

Thread FORMS elements as the first argument of their successor.
Example:
(thread-first
5
(+ 20)
(/ 25)
-
(+ 40))
Is equivalent to:
(+ (- (/ (+ 5 20) 25)) 40)
Note how the single `-' got converted into a list before
threading.