# extended real numbers

## Primary tabs

Defines:
plus infinity, minus infinity, $\overline{\mathbb{R}}$, infinite, infinity, finite
Type of Math Object:
Definition
Major Section:
Reference
Parent:
Groups audience:

## Mathematics Subject Classification

### What is wrong with this latex code

PM reports that an error in this file:
---------------------------------------------
66: \begin{eqnarray*}
67: (a,\infty] &=& \{ x\in \sR : x>a \}, \\
68: [-\infty,a) &=& \{ x\in \sR : x>a \}.
69: \end{eqnarray*}
70:
!!! Missing  inserted

\sR is defined as
\newcommand{\sR}[0]{\mathbb{R}}
and that works fine elsewhere in the entry.
---------------------------------------------
I can't see any problem, and the entry renders fine without
these lines.

Any ideas?

### Re: What is wrong with this latex code

Array enviroments have a problem with having a [ as the first character of a new line as you can use [ <measurement> ] to set the gap between lines (or something). You might try replacing line 68 with

68: {[}-\infty, a)........

### Re: What is wrong with this latex code

silverfish wrote:

> 68: {[}-\infty, a)........

I think you also need {-\infty} rather than -\infty in order for the spacing to come out correctly.

### Re: What is wrong with this latex code

That does it. Thanks!