How to use ForwardDiff?

I’m trying to learn how to use autodifferentiation for the first time since that came up in something else. What am I doing wrong?

using ForwardDiff
f(x) = 2x
g = x -> ForwardDiff.gradient(f, x)
# DimensionMismatch("gradient(f, x) expects that x is an array. Perhaps you meant derivative(f, x)?")

Why does this give a dimension mismatch error? Thanks

you probably want the derívative, rather than the gradient.

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