Mention that RNDN is the "ties toward even" version in RealField

[jasongrout]

The IEEE754 standard has two versions of "round to nearest". It appears that ours is the "ties toward even" version (see http://www.mpfr.org/mpfr-current/mpfr.html#MPFR-Basics). We ought to mention this in the docs to RealField when it talks about the rounding modes.

CC: @robertwb @sagetrac-mvngu

Component: documentation

Author: Jason Grout

Reviewer: Minh Van Nguyen

Merged: sage-4.3.2.alpha0

Issue created by migration from https://trac.sagemath.org/ticket/7802

[jasongrout]

comment:1

Attachment: trac-7802-ties-to-even-doc.patch.gz

[sagetrac-mvngu]

Reviewer: Minh Van Nguyen

[sagetrac-mvngu]

Author: Jason Grout

[sagetrac-mvngu]

comment:2

Looks good. Applies OK against Sage 4.3.1.rc1. Just make sure you first merge #7999 before applying trac-7802-ties-to-even-doc.patch. Otherwise, the HTML version of the reference manual won't build successfully.

[sagetrac-mvngu]

Merged: sage-4.3.2.alpha0