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Improved doc for polynomial ring element constructors #2179

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Improved doc for polynomial ring element constructors #2179

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8cecaa6
Improved doc for polynomial ring element constructors
JohnAAbbott Oct 1, 2025
c3d5230
Now recommends map_coefficients over evaluation
JohnAAbbott Oct 6, 2025
19800b4
Update docs/src/polynomial.md
JohnAAbbott Oct 6, 2025
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6 changes: 5 additions & 1 deletion docs/src/polynomial.md
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Expand Up @@ -95,8 +95,12 @@ the usual ways of constructing an element of a ring.
(R::PolyRing)(c::elem_type(R))
(R::PolyRing{T})(a::T) where T <: RingElement
```
The third constructor above cannot be used to coerce a polynomial from one ring
to another; instead use evaluation, for instance: `f(y)` where `y` is the
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@fingolfin fingolfin Oct 1, 2025

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But evaluation is not the best way. We can mention it, but really should be recommending map_coefficient here, ideally with a jldoctest usage example.

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@JohnAAbbott JohnAAbbott Oct 6, 2025

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I confirm that evaluation is impressively slow (and requires impressively much RAM): for the record, I tried mapping (x+1)^99999 from ZZ[x] to ZZ[y], and gave up after 600s CPU -- map_coefficients took less than 1s.

generator of the destination polynomial ring. The fourth constructor creates
a constant polynomial from an elements of the coefficient ring.

For polynommials there is also the following more general constructor accepting
For polynomials there is also the following more general constructor accepting
an array of coefficients.

```julia
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