# Why does bm fail for DeclareMathOperator

I like the bm package. However, it seems to me the line

\DeclareMathOperator{\curl}{\bm{curl}}


won't make curl bold. Although changing bm to mathbf will do the job, I have to use mathbf everytime afterwards to keep consistency, which is something I'd like to avoid. Are there any solutions to that?

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– yo'
Feb 2 '15 at 14:24

The definitions are the wrong way round.

You want something like

\DeclareMathOperator{\curlinternal}{curl}
\bmdefine\curl{\bm{\curlinternal}}


Or you could save TeX some work figuring out what that means and do

\newcommand\curl{\mathop{\mathbf{curl}}}


PS of course you like the bm package:-)
• Isn't it \mathop{{}\mathbf{curl}}?
• @yo' my eyes are not as good as they once were, but I reckon there is more than 1 letter in curl Feb 2 '15 at 14:35
• Ah, I always miss something with \mathop, thanks for clarifying.
• @DavidCarlisle -- this construction isn't blindingly obvious. in fact, reading the output of texdoc bm it still is neither blindingly obvious, nor even hinted at. why don't you do a good deed and add it. please? Nov 13 '15 at 21:26