[math-fun] notation query

22 Sep 2013

      I read a paper today which used a notation I do not remember seeing
before; I'm curious whether it is common.

The paper discussed the union of the reals with a pair of points at
infinity by using an overbar over the set R.  It didn't explain the
notation, but it was clear from the context.

For those with utf-8 support:

    ℝ̅ ≡ ℝ ⋃ { −∞, +∞ }

or in TeX:

    \bar{\mathbb{R}}  \def \mathbb{R} \bigcup \{ -\inf, +\inf \}

or maybe \overling{\mathbb{R}}.

Is that common?

Thanks.

-JimC
-- 
James Cloos <cloos@jhcloos.com>         OpenPGP: 1024D/ED7DAEA6