Anonymous argument (AA) is an argument without a name. 

w/o AA:

func :: a -> a -> a -> a

func aa0 aa1 aa2 = aa0 `op` aa1 `op` aa2

\aa0 aa1 aa2 -> aa0 `op` aa1 `op` aa2

w/ AA:

func :: a -> a -> a -> a

func = \0 `op` \1 `op` \2

\-> \0 `op` \1 `op` \2

AA syntax: '\n', where n is one of the (0 1 2 3 4 5 6 7 8 9). 'n' corresponds to the position of a parameter.

I think a language shouldn't force you to invent names for things that are used only once, same philosophy as with an anonymous function.

Is this feature needed? Does something like this already exist?