Merge pull request #160 from jverzani/issue_159

close issue 159

Author: jverzani

src/Polynomials.jl

@@ -564,7 +564,7 @@ function _polyder(p::Poly{T}, order::Int=1) where {T}
   n = length(p)
   a2 = Vector{T}(undef, n-order)
   for i = order:n-1
-    a2[i-order+1] = p[i] * prod((i-order+1):i)
+    a2[i-order+1] = reduce(*, (i-order+1):i, init=p[i])
   end
 
   return Poly(a2, p.var)

test/runtests.jl

@@ -391,3 +391,5 @@ xx = Real[20.0, 30.0, 40.0]
 yy = Real[15.7696, 21.4851, 28.2463]
 polyfit(xx,yy,2)
 
+## Issue with overflow and polyder Issue #159
+@test !iszero(polyder(Poly(BigInt[0, 1])^100, 100))