mjo-proof_by_cases.tex

   1 %
   2 % A proof-by-cases environment. This gives you a nicely-indented list
   3 % of cases for use in proofs.
   4 %
   5 % Example:
   6 %
   7 % Case 1 (x >= 0): herp.
   8 %
   9 % Case 2 (x < 0): derp.
  10 %
  11
  12 % Used below to define pcases.
  13 \usepackage{enumitem}
  14
  15 % Using the enumitem package, we define a new type of list, called
  16 % ``pcases'' (proof by cases). Each case has a label with an arabic
  17 % numeral (the case number), but also a \thiscase identifier. The
  18 % macro \thiscase is defined below by the \case command, and gives the
  19 % name or conditions or whatever that distinguish one case from
  20 % another.
  21 \newlist{pcases}{enumerate}{1}
  22 \setlist[pcases]{
  23   label=\textbf{Case~\arabic*}:~\protect\thiscase\textbf{.},
  24   ref=\arabic*,
  25   align=left,
  26   leftmargin=0pt,
  27   listparindent=\parindent,
  28   parsep=\parskip,
  29   itemsep=\baselineskip}
  30
  31 % The optional argument here gets stuffed into the \thiscase macro, to
  32 % be called by pcases when it creates this list item. The \hfill is a
  33 % hack intended to force the proof to start on a new line, rather than
  34 % right after the colon. A \newline where the \hfill is does not work,
  35 % so we consume the rest of the line instead.
  36 \newcommand{\case}[1][]{
  37   \def\thiscase{#1}%
  38   \item \hfill\par\vspace{\baselineskip}
  39 }