disallow non exact fields for the 'field' backend

[videlec]

The 'field' backend does not properly support non exact fields

sage: omega = 2*RR.pi() / 5
sage: verts = [((i*omega).sin(), (i*omega).cos()) for i in range(5)]
sage: verts
sage: Polyhedron(vertices=verts, base_ring=RR)
Traceback (most recent call last):
...
AssertionError: 

or

sage: Q = polytopes.icosahedron()
sage: Q = polytopes.icosahedron(); Q
A 3-dimensional polyhedron in (Number Field in sqrt5 with defining polynomial x^2 - 5)^3 defined as the convex hull of 12 vertices
sage: Q_RR = Polyhedron(vertices = [n(v.vector(),digits=10) for v in Q.vertices()])
sage: Q_RR
A 3-dimensional polyhedron in (Real Field with 37 bits of precision)^3 defined as the convex hull of 7 vertices
sage: Q_RR = Polyhedron(vertices = [n(v.vector(),digits=30) for v in Q.vertices()])
sage: Q_RR
A 3-dimensional polyhedron in (Real Field with 103 bits of precision)^3 defined as the convex hull of 1 vertex and 3 rays

We simply raise an error if somebody want to try this.

CC: @fchapoton @jplab @mkoeppe

Component: geometry

Keywords: bug, days84

Author: Vincent Delecroix

Branch: c28fcf0

Reviewer: Jean-Philippe Labbé

Issue created by migration from https://trac.sagemath.org/ticket/18220

[videlec]

Changed keywords from none to bug

[mkoeppe]

comment:2

Another bug for RDF polyhedra: #21270

[jplab]

Description changed:

--- 
+++ 
@@ -14,3 +14,17 @@
     313         self.vertices = vertices
 AssertionError: 
 ```
+
+There are also other types of wrong behavior:
+
+```
+sage: Q = polytopes.icosahedron()
+sage: Q = polytopes.icosahedron(); Q
+A 3-dimensional polyhedron in (Number Field in sqrt5 with defining polynomial x^2 - 5)^3 defined as the convex hull of 12 vertices
+sage: Q_RR = Polyhedron(vertices = [n(v.vector(),digits=10) for v in Q.vertices()])
+sage: Q_RR
+A 3-dimensional polyhedron in (Real Field with 37 bits of precision)^3 defined as the convex hull of 7 vertices
+sage: Q_RR = Polyhedron(vertices = [n(v.vector(),digits=30) for v in Q.vertices()])
+sage: Q_RR
+A 3-dimensional polyhedron in (Real Field with 103 bits of precision)^3 defined as the convex hull of 1 vertex and 3 rays
+```

[videlec]

New commits:

c28fcf0

18220: raise an error for non exact fields

[videlec]

Description changed:

--- 
+++ 
@@ -1,3 +1,4 @@
+The 'field' backend does not properly support non exact fields
 
 ```
 sage: omega = 2*RR.pi() / 5
@@ -6,16 +7,9 @@
 sage: Polyhedron(vertices=verts, base_ring=RR)
 Traceback (most recent call last):
 ...
-/sage/local/lib/python2.7/site-packages/sage/geometry/polyhedron/double_description_inhomogeneous.pyc in _extract_Vrep(self, DD)
-    309         vertices = []
-    310         for v in R1 + L1:
---> 311             assert v[0] == 1
-    312             vertices.append(v[1:])
-    313         self.vertices = vertices
 AssertionError: 
 ```
-
-There are also other types of wrong behavior:
+or
 
 ```
 sage: Q = polytopes.icosahedron()
@@ -28,3 +22,5 @@
 sage: Q_RR
 A 3-dimensional polyhedron in (Real Field with 103 bits of precision)^3 defined as the convex hull of 1 vertex and 3 rays
 ```
+
+We simply raise an error if somebody want to try this.

[videlec]

Branch: u/vdelecroix/18220

[videlec]

Commit: c28fcf0

[videlec]

Author: Vincent Delecroix

[videlec]

Changed keywords from bug to bug, days84