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Bugfix in Horner's scheme #79

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Dec 12, 2016
+9 −1
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Bugfix in Horner's scheme #79

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2 changes: 1 addition & 1 deletion src/Polynomials.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -368,7 +368,7 @@ function polyval{T,S}(p::Poly{T}, x::S)
if lenp == 0
return zero(R) * x
else
y = convert(R, p[end]) + zero(T)*x
y = convert(R, p[end])
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I don't understand why zero(T)*x is here. If there is any reason, perhaps changing to zero(T)*zero(x)?

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actually, I do not see any benefit in using zero(T)*zero(x). since we have convert(R, p[end]) where R = promote_type(T,S), zero(x) will be automatically promoted to R. For normal numbers, I mean standard Numbers, zero(x) is not needed at all. Then, if there is a custom type Type <: Number, it might make sense to use zero(x) and rely on the conversion rules among Numbers.

What do you think?

Do you think we can push these issues (i.e., Horner's bug, Base./ and perhaps polyder) this weekend?

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I feel the same way, but didn't write this so may be missing something. As for time, yes if no one chimes in I'll merge the first two in a few days.

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thanks! that'd be great! :)

for i = (endof(p)-1):-1:0
y = p[i] + x*y
end
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8 changes: 8 additions & 0 deletions test/runtests.jl
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Expand Up @@ -250,3 +250,11 @@ r = Poly([1.0, 2, 3])
p = poly([1,2,3])
q = poly([1,2,3])
@test hash(p) == hash(q)

## Check for Inf/NaN operations
p1 = Poly([Inf, Inf])
p2 = Poly([0, Inf])
@test p1(Inf) == Inf
@test isnan(p1(-Inf))
@test isnan(p1(0))
@test p2(-Inf) == -Inf