const ħc = 197.33 # MeVfm
const r_reg = 1E-8 # fm # regulator for R

"Integrate a uniformly discretized function f using Simpson's rule where h is the step size and coefficient is an optional scaling factor."
function simpsons_integrate(f::AbstractVector{Float64}, h::Float64; coefficient::Float64 = 1.0)
    @assert length(f) % 2 == 1 "Number of mesh divisions must be even for Simpson's rule"
    s = sum(enumerate(f)) do (i, fi)
        if i == 1 || i == length(f)
            return fi
        elseif i % 2 == 0
            return 4fi
        else
            return 2fi
        end
    end
    return (h/3) * coefficient * s
end