I cant get it to work

[xArthasx]

I have osx el capitan and Emacs 24.5.1 (x86_64-apple-darwin15.2.0, NS apple-appkit-1404.34)
I get this error and the line is completely black.

Debugger entered--Lisp error: (void-function reduce)
reduce(+ ("") :key length)
airline-shorten-directory("" 30)
#nil "\303\304\305 \304Q\306\307\310\311!\312\313\311!F#\303\314�!\304P\306\307\313\311!\312\313\315!F# \316=\203>�\303\317\320 \n"\304P\306\307\310\315!\312\313\315!F#\202P�\303\321\320 !\304P\306\307\310\315!\312\313\315!F#\303\314�!\304P\306\307\313\315!\312\313\322!F#\303\323\320 !\304P\306\307\310\322!\312\313\322!F#\303\314�!\260�\306\307\313\322!D#\303\324\306\325#\260�\207" [airline-utf-glyph-separator-left airline-display-directory airline-shortened-directory-length propertize " " eshell/whoami face :foreground face-foreground airline-insert-outer :background face-background char-to-string airline-insert-inner airline-directory-shortened airline-shorten-directory eshell/pwd abbreviate-file-name airline-insert-center airline-curr-dir-git-branch-string " $ " nil] 12
eshell-emit-prompt()
run-hooks(eshell-post-command-hook)
eshell-mode()
eshell(nil)
call-interactively(eshell record nil)
command-execute(eshell record)
execute-extended-command(nil "eshell")
call-interactively(execute-extended-command nil nil)
command-execute(execute-extended-command)

[xArthasx]

I just found the solution, right after i psoted this.
(require 'cl)