What does the `<<` operator mean in elm?

Question

In the following code taken from Elm Form Example, line 122, what does the << operator mean?

Field.field Field.defaultStyle (Signal.send updat         


        

Answer 1

Explantion for javascript developers:

--elm

(a << b) x

Will be similar

//javasript

a(b(x))

<< or >> is called function composition