lambda - Not Function And Function Composition in F# -

is possible f# have function composition between operators.not , standard .net function, instance string.isnullorempty?

in other words, why following lambda expression unacceptable:

(fun x -> not >> string.isnullorempty) 

the >> function composition works other way round - passes result of function on left function on right - snippet passing bool isnullorempty, type error. following works:

(fun x -> string.isnullorempty >> not) 

or can use reversed function composition (but think >> preferred in f#):

(fun x -> not << string.isnullorempty) 

aside, snippet creating function of type 'a -> string -> bool, because ignoring argument x. suppose might want just:

(string.isnullorempty >> not)