[Xy-pic] Math fonts

Yannick Delbecque yannick.delbecque at mail.mcgill.ca
Mon May 5 19:22:36 CEST 2003

I have many times ran into trouble when using some math fonts in 

For example when running LaTeX on the command
\[ \xymatrix{ \mathbb{R} \ar[r]^{d} & \mathbb{R} } \]

I get the following error (twice):

! You can't use `\spacefactor' in math mode.
\@ ->\spacefactor
l.19 \xy@{\save }{\save@ }

Stangely, if I try instead
\[ \xymatrix{ \ensuremath{\mathbb{R}} \ar[r]^{d} & 
\ensuremath{\mathbb{R}}} \]
then everything works fine.

I did try to find an explanation of this in both the user guide and the 
reference manual without success. I fear I missed something obvious. 
Does someone have an explanation?


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