Opened 3 months ago

Closed 3 months ago

#30267 closed defect (fixed)

Coercion via restriction of chart functions

Reported by: gh-mjungmath Owned by:
Priority: major Milestone: sage-9.2
Component: manifolds Keywords:
Cc: egourgoulhon, tscrim Merged in:
Authors: Michael Jung Reviewers: Travis Scrimshaw, Eric Gourgoulhon
Report Upstream: N/A Work issues:
Branch: d494bbd (Commits) Commit: d494bbd912c42ca2386664c597b15de117dd52a9
Dependencies: Stopgaps:

Description

At this stage, scalar fields (and tensor fields) support coercions via restrictions: 

sage: M = Manifold(2, 'M')
sage: c.<x,y> = M.chart()
sage: D = M.open_subset('D')
sage: A = M.scalar_field_algebra(); A_D = D.scalar_field_algebra()
sage: A_D.has_coerce_map_from(A)
True

But the chart function ring does not support that coercion, even for derived charts: 

sage: c_D = c.restrict(D, x^2+y^2<1)
sage: R = c.function_ring(); R_D = c_D.function_ring()
sage: R_D.has_coerce_map_from(R)
False

Consequently, this should be treated the same way as scalar fields since chart functions are the very foundation of scalar fields.

I suggest we add that coercion in case one chart (here c_D) is the restriction of the other (here c).

Change History (10)

comment:1 Changed 3 months ago by gh-mjungmath

  • Authors set to Michael Jung
  • Status changed from new to needs_review

comment:2 Changed 3 months ago by gh-mjungmath

  • Branch set to u/gh-mjungmath/coercion_via_restriction_of_chart_functions

comment:3 Changed 3 months ago by git

  • Commit set to 4bcd2eeb367909eef66de8f0390f4fa7abea22c9

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

​4bcd2eeTrac #30267: coercion via restriction added

comment:4 Changed 3 months ago by tscrim

  • Reviewers set to Travis Scrimshaw
  • Status changed from needs_review to positive_review

LGTM.

comment:5 Changed 3 months ago by gh-mjungmath

Thanks.

comment:6 follow-up: Changed 3 months ago by egourgoulhon

Thanks for this ticket. May I suggest to correct a typo: 

-    The ring of all chart function w.r.t. to a chart::
+    The ring of all chart functions w.r.t. to a chart::

comment:7 Changed 3 months ago by git

  • Commit changed from 4bcd2eeb367909eef66de8f0390f4fa7abea22c9 to d494bbd912c42ca2386664c597b15de117dd52a9
  • Status changed from positive_review to needs_review

Branch pushed to git repo; I updated commit sha1 and set ticket back to needs_review. New commits:

​d494bbdTrac #30267: docstring typo fixed

comment:8 in reply to: ↑ 6 Changed 3 months ago by gh-mjungmath

Replying to egourgoulhon:

Thanks for this ticket. May I suggest to correct a typo: 

-    The ring of all chart function w.r.t. to a chart::
+    The ring of all chart functions w.r.t. to a chart::

Done. Thank you.

comment:9 Changed 3 months ago by tscrim

  • Reviewers changed from Travis Scrimshaw to Travis Scrimshaw, Eric Gourgoulhon
  • Status changed from needs_review to positive_review

comment:10 Changed 3 months ago by vbraun

  • Branch changed from u/gh-mjungmath/coercion_via_restriction_of_chart_functions to d494bbd912c42ca2386664c597b15de117dd52a9
  • Resolution set to fixed
  • Status changed from positive_review to closed
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