Floor (integer) division of reals and rationals

[nathanncohen]

As reported in [1] and [2]

sage: x = 1/2 
sage: x//2 
1/4
sage: RDF(5) // 2
2.5
sage: RIF(5) // 2
TypeError: unsupported operand type(s) for //: 'sage.rings.real_mpfi.RealIntervalFieldElement' and 'sage.rings.real_mpfi.RealIntervalFieldElement'
sage: QQ(7) // QQ(3)
7/3

[1] https://groups.google.com/d/topic/sage-support/xE_S3WbFHzA/discussion
[2] https://groups.google.com/d/msg/sage-devel/nQDAMtqnEsY/HfpIdvc9AwAJ

Depends on #2034

CC: @williamstein @sagetrac-tmonteil @zimmermann6

Component: basic arithmetic

Author: Jan Keitel, Jeroen Demeyer

Branch/Commit: u/jdemeyer/ticket/15260 @ 616f88c

Reviewer: Jeroen Demeyer, Thierry Monteil

Issue created by migration from https://trac.sagemath.org/ticket/15260

[sagetrac-tmonteil]

comment:1

The reason is that for rationals (and apparently more generally for FieldElement), we have

    def __floordiv__(self, other):
        return self / other

where it should be

    def __floordiv__(self, other):
        return floor(self / other)

I will do a patch once i have compiled a more recent version of Sage

What is fun is that

sage: RDF(0.5)//2
0.25

sage: RR(0.5)//2
TypeError: unsupported operand type(s) for //: 'sage.rings.real_mpfr.RealLiteral' and 'sage.rings.real_mpfr.RealNumber'

[sagetrac-jkeitel]

Author: Jan Keitel

[sagetrac-jkeitel]

comment:4

Here's a branch that does this and implements a simple floordiv method for RR.

---

New commits:

c9146be	Fix floordiv of FieldElements.
fd78ca5	Floordiv for real_mpfr.

[sagetrac-jkeitel]

Branch: u/jkeitel/15260

[sagetrac-jkeitel]

Commit: fd78ca5

[jdemeyer]

Changed branch from u/jkeitel/15260 to u/jdemeyer/ticket/15260