[julia-users] how to pass function as argument?

[cnbiz850]

Say I want to pass the following function f1 to a function called f2 as 
an argument.  What is exactly the type of function f1?  How do I define 
f2's arguments?

function f1(i::Int, x::Float)
    x = 10. * i
    nothing
end
function f2(f1::???)
end