```
x <- c(-2, -1, 0, 1, 2)
p <- c(1, 0, 1) # polynomial x^2 + x, derivative 2*x
horner(p, x)$y #=> 5 2 1 2 5
horner(p, x)$dy #=> -4 -2 0 2 4
p <- Poly(c(1, 2, 3)) # roots 1, 2, 3
hornerdefl(p, 3) # q = x^2- 3 x + 2 with roots 1, 2
```

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