# Meaning of mathematical operator that consists of square brackets with a plus sign as a subscript

I was reading a paper on tomographic reconstruction, and I found an operator that is not explained:

$[expression]_+$

The operator was used to compute a surrogate for the log-likelihood cost function. I do not know what that operator means. I've seen brackets without that plus sign before that were used to represent the rounding operation.

Thanks!

Edit: I've been looking at http://www.latexsearch.com and I found some results where $[x]_+:=\text{max}\{0,x\}$, and I think this agrees with how the paper uses it.

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What paper? ${}{}$ –  Qiaochu Yuan Oct 16 '12 at 23:08
"Ordered subsets algorithms for transmission tomography" by Erdogan and Fessler. Phys. Med. Biol. 44 (1999) 2835–2851 –  Damian Oct 16 '12 at 23:10
@damian you can post your finding in an answer if you want, so people can see it solved –  Jean-Sébastien Oct 17 '12 at 1:40

Looking at other papers I found through Latex search, I found that the bracket operator is defined as: $[x]_+=\max\{0,x\}$