Quadrature from x=0 to x=Inf?

General Usage
10

It is:

julia> function poisson(x,λ=1)
           if isnan(λ^x*exp(-λ)/gamma(x+1))
               @show λ^x; @show exp(-λ); @show gamma(x+1)
           end
           return λ^x*exp(-λ)/gamma(x+1)
       end
poisson (generic function with 2 methods)

julia> poisson(1871.5213495195621,2)
λ ^ x = Inf
exp(-λ) = 0.1353352832366127
gamma(x + 1) = Inf
NaN

You have Inf/Inf

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