# clarification on the use of @{} with table headings?

Most examples I've seen are like this:

\begin{tabular}{@{}l r r@{}}


that is, with one @{} to the left of first column specifier and another @{} to the right of the last column specifier.

Yet the "Not So Short Guide to LaTex" says this construct suppresses the leading space.

I'm a bit confused. Which of the following interpretations are correct?

• @{} suppresses the space on the side of the column specifier where it is placed (i.e. placed to the left of the specifier it suppresses the leading space and, conversely, placed to the right it suppresses the trailing space)

• only @{} should be placed to the left of the first column and/or to the right of the last column, but not in between.

• neither of the above.

Unfortunately I'm not at a computer with LaTeX at this very moment so I cannot try it instead of asking.

Thanks a lot.

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@{}suppresses the space between columns, that means after the preceding column and before the next. This way it affects also the space before the first column and after the last, if positioned there.

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Incidentally, this is a good trick to use when you have "complicated" numbers. Use \begin{tabular}{lr@{.}l} Variable 1 & -2&35 \\ Variable 2 & 127&50*** ...

The "." in the braces of "@{.}" uses a decimal point to separate columns 2 and 3 with no space. So you get -2.35 and 127.50*** aligned at the decimal points. This is difficult to do another way because the numbers are different orders of magnitude, one is negative, and one is marked as significant using stars.

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In germany, one would have to say @{,} i suspect? Or will it be locale aware? (I think latex does not care what is between the braces?) – Johannes Schaub - litb Aug 14 '10 at 21:24
The dcolumn package <ctan.org/pkg/dcolumn>; is designed to help with aligning columns of numbers at the decimal point. – Martin Heller Aug 14 '10 at 21:41
Right, you could put anything in there, so you should use a comma if that's your preferred separator. Thanks for the info, Martin, I'll check that out. – Charlie Aug 15 '10 at 0:09
@Johannes Schaub You will need to say @{,} in Germany. You can actually use it with any symbol. I use it often with @{=} to align descriptions for symbols, rather than use a math environment. – Yiannis Lazarides Sep 4 '10 at 14:23
@Yiannis: That's going to produce incorrect spacing (i.e. none) around the relational symbol. I'm not sure exactly how you're using it, but that seems wrong. – TH. Sep 4 '10 at 20:28