The memoir class - The UK TeX Archive

11. ROWS AND COLUMNS\[ \begin{array}({cc})a&b\\c&d\end{array} \]Or, a litle more complex\[ \begin{array}({c})\begin{array}|{cc}|x_{1} & x_{2} \\x_{3} & x_{4}\end{array} \\y \\z\end{array} \](a b)c d⎛∣ x ∣ ⎞1 x 2 ∣∣∣⎜ x 3 x 4 ⎟⎝ y ⎠zAnd you can do things like this:\[ a = {\begin{array}|{*{20}{c}}|x-\lambda & 1 & 0 \\0 & x-\lambda & 1 \\0 & & x-\lambda \\\end{array}}^{2} \]a =∣x − λ 1 00 x − λ 10 x − λAs another example, a construct equivalent to plain TeX’s \cases could be defined by:\[ f(x)=\begin{array}\{{lL}.0 & if $x=0$\\\sin(x)/x & otherwise\end{array} \]∣{0 if x = 0f(x) =sin(x)/x otherwiseHere L denotes a column of left aligned L-R text, as described earlier. Note that as thedelimiters must always be used in pairs, the ‘.’ must be used to denote a ‘null delimiter’.This feature is especially useful if the [t] or [b] arguments are also used. In thesecases the result is not equivalent to surrounding the environment by \left. . . \right, ascan be seen from the following example:2214