# Left-right spacing of parentheses with DeclarePairedDelimiter

I know that \big and similar commands cause an incorrect spacing between the delimiter and their contents, and they should be replaced with \bigl and so on. I've defined some commands with \DeclarePairedDelimiter, but it seems to me that this macro doesn't use the left-right distinguished variants of \big (and the like) but the generic \big command. The mathtools manual doesn't cover this question, so I ask you. How can I make \DeclarePairedDelimiter with \bigr and \bigl?

For example, I have defined

\DeclarePairedDelimiter{\norm}{\lVert}{\rVert}
\DeclarePairedDelimiterX{\inner}[2]{\langle}{\rangle}{{#1},{#2}}
\DeclarePairedDelimiter{\parentheses}{(}{)}

but I don't know, using \norm[\big]{x} whether it will be expanded as \big\lVert{x}\big\rVert or \bigl\lVert{x}\bigr\rVert. Maybe \rVert and \lVert already take care by themselves of the correct spacing, but there's still the last one with ( and ).

• This is more of a general question, I don't have an issue on a particular piece of code. Anyway, I'll post an example. – yellon Apr 4 '16 at 18:53
• Actually, mathtools will translate \norm[\big]{x} into \mathopen{\big\lVert}x\mathclose{\big\rVert}. And \bigl\lVert is defined to do \mathopen{\big\lVert} (similarly for \bigr), so it's exactly the same. – egreg Apr 4 '16 at 20:04