#15618: convert_map should not be a map
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Reporter: pbruin | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.1
Component: coercion | Keywords: conversion map
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
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The following example shows that at least some convert_maps are
incorrectly assumed to be homomorphisms:
{{{
sage: f = GF(11).convert_map_from(GF(7))
sage: f
Conversion map:
From: Finite Field of size 7
To: Finite Field of size 11
sage: f.parent()
Set of field embeddings from Finite Field of size 7 to Finite Field of
size 11
}}}
This has the effect of constructing an element of a set that is in fact
empty.
Moreover, conversions should in general not be maps, because they are not
necessarily defined everywhere.
See also https://groups.google.com/forum/#!topic/sage-devel/Z4iNgVMFoms
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Ticket URL: <http://trac.sagemath.org/ticket/15618>
Sage <http://www.sagemath.org>
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