Confused about the anonymous function in julia

Question

I have this code:

Using ForwardDiff:gradient
derivative(f,x) = gradient(x->f(x[1]),[x])

I know gradient in the ForwardDiff take a vector as argument, but what does this mean: (x->f(x[1])), I am confused by x[1].

Answer 1

I am confused by x[1]

It means to take the first element of the vector x.

This code doesn't really make much sense with the [x] as the last argument. You should probably just use e.g.:

julia> ForwardDiff.derivative(sin, 1.0)
0.5403023058681398