Khan/KaTeX — pull request #87 by kasperpeulen (2014-09-19 14:37:54+00:00)
Title: add mathbb macro

okay, this is quite some changes
but I think in this way it also possible to add mathcal, and mathfrak easily

I've implemented it so that it also accepts letters, so that \mathbb{REAL} works, but \mathbb{A+B} wont work. I LaTeX self, you get strange ouput if you do something like \mathbb{R^n} for example:

I think it is better to just give an error message, saying that it expected a letter.