Meaning of R++

Date: 9/12/96 at 13:41:50
From: Alexander Cook
Subject: Meaning of R++

Dear Dr. Math,

What do the symbols R_{+} and R_{++} mean?
I have never seen this notation before. Please, tell me.

Alexander Cook

Date: 9/13/96 at 11:22:55
From: Doctor Ken
Subject: Re: Meaning of R++

Hello!

The symbol R_+ means "all real numbers x such that x > 0."  I'm not 
sure what R_++ means, but it's probably something like R_+, and maybe 
now you can figure it out based on the context.  It might be worth 
noting that sometimes, in some books, the authors use R_+ to mean 
"all real numbers x such that x >= 0 (greater than or equal to)," but 
it's more standard to mean greater than (at least in America). 

-Doctor Ken,  The Math Forum
 Check out our web site!  http://mathforum.org/dr.math/