[Tex/LaTex] Empty clause symbol

math-modesymbols

This is a very simple question. I was wondering if anybody might know of a way to generate the symbol for the empty clause in LaTeX (small, character-sized empty square). By “empty clause" I am referring to the propositional / first-order logic symbol which denotes a clause that is unsatisfiable by default, and is the result of a refutation from a set of unsatisfiable clauses.

Best Answer

You have several options available. Some predefined squares or a hand-made one

\newcommand{\Hsquare}{%
  \text{\fboxsep=-.2pt\fbox{\rule{0pt}{1ex}\rule{1ex}{0pt}}}%
}

(requires \usepackage{amsmath}). Here's a table with some of the squares:

enter image description here

In the second column you find what package provides the symbol (next to \Hsquare I could have added amsmath, which is however not a font package). Note that you should say \text{\Squarepipe} if you decide for that symbol.