Coercion issue with Laurent polynomial rings

[mezzarobba]

sage: coercion_model.common_parent(Frac(QQ['t']), LaurentPolynomialRing(CC,'t'))
Fraction Field of Univariate Polynomial Ring in t over Rational Field

Component: coercion

Author: Frédéric Chapoton

Branch/Commit: 8d97f9d

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/31320

[fchapoton]

comment:1

more data

sage: cm = coercion_model
sage: cm.explain(Frac(QQ['t']), LaurentPolynomialRing(CC,'t'))                  
Coercion on right operand via
    Conversion via converter map:
      From: Univariate Laurent Polynomial Ring in t over Complex Field with 53 bits of precision
      To:   Fraction Field of Univariate Polynomial Ring in t over Rational Field
Arithmetic performed after coercions.
Result lives in Fraction Field of Univariate Polynomial Ring in t over Rational Field
Fraction Field of Univariate Polynomial Ring in t over Rational Field

[mkoeppe]

comment:2

Moving to 9.4, as 9.3 has been released.

[fchapoton]

New commits:

ed5f0ca

fix coercion of Laurent into fraction fields

[fchapoton]

Author: Frédéric Chapoton

[fchapoton]

Branch: u/chapoton/31320

[fchapoton]

Commit: ed5f0ca

[tscrim]

comment:6

Subtle, but a good catch. Green bot => positive review.

[tscrim]

Reviewer: Travis Scrimshaw

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

8d97f9d

another fix

[sagetrac-git]

Changed commit from ed5f0ca to 8d97f9d

[fchapoton]

comment:8

I had to change the correction, but now the bot is green.

The issue was about the existence of a morphism from Laurent[t]/QQ to Frac(ZZ[t]).

May I switch to positive ?

By the way, thanks a lot for your reviews, Travis. Domo arigato.

[tscrim]

comment:9

No problem. Thank you for all your work on improving Sage, especially the code and doc polishing.

[vbraun]

Changed branch from u/chapoton/31320 to 8d97f9d