I'm trying to use \cdotas a dummy for a function argument in the following expression


However, the above produces more space to the right of the dot than to the left. I'd like the spacing to be symmetrical. I've tried using {}on either side but haven't been able to get the desired result.

  • This question is quite similar. Maybe it answers your question too.
    – hbaderts
    Aug 17, 2015 at 8:45
  • 1
    The trouble is not with \cdot but with \mid, which is a relation. You would get equal (but small) spacing using {\mid}, but I wouldn't suggest that. Isn't C(\,\cdot\mid\mathcal{F}_{t-1}) enough?
    – campa
    Aug 17, 2015 at 8:45
  • That is better but still not perfectly symmetrical. Perhaps it would be better to use an alternative to \mid that isn't a relation. I'm just not sure such a thing exists. Aug 17, 2015 at 8:48

1 Answer 1


Since you want to use the blank next either between an opening atom (the open parenthesis) and a relation atom (\mid) or between a relation atom and a closing atom, you can define \blank to be a relation symbol:




$C(\blank \mid F_{t-1})$

$C(x \mid \blank)$


The trick is that TeX doesn't add space in cases

Open Rel Rel


Rel Rel Close

enter image description here

  • If \blank is to be used in a different context, such as “blank+x”, then {\blank}+x should do.
    – egreg
    Aug 17, 2015 at 9:10
  • Why not just make the widened \cdot an ord here? Then it would be in the same category as x. Aug 20, 2015 at 12:10
  • @AndrewSwann The spacing would be asymmetric. It would be right if instead of \mid a comma was used.
    – egreg
    Aug 20, 2015 at 15:12

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