The memoir class - The UK TeX Archive

E. LATEX AND TEXHalf Dome in Yosemite or the North Face of the Eiger without having first gained experienceon friendlier rocks.The LaTeX kernel is full of internal commands and a few are mentioned in Lamport.There is no place where you can go to get explanations of all the LaTeX commands, but ifyou run LaTeX on the source2e.tex file which is in the standard LaTeX distribution youwill get the commented kernel code. The index of the commands runs to about 40 doublecolumn pages. Each class and package introduce new commands over and above those inthe kernel.LaTeX includes \newcommand, \providecommand and \renewcommand as means of(re-)defining a command, but TeX provides only one method.\def〈cmd〉〈arg-spec〉{〈text〉}\def specifies that within the local group the command \cmd is defined as 〈text〉, and anyprevious definitions of 〈cmd〉 within the group are overwritten. Neither the 〈text〉 nor anyarguments can include an end-of-paragraph. The LaTeX equivalent to \def is the pair ofcommands \providecommand* followed by \renewcommand*.The 〈arg-spec〉 is a list of the argument numbers (e.g., #1#2) in sequential order, the listending at the ‘{’ starting the 〈text〉. Any spaces or other characters in the argument list aresignificant. These must appear in the actual argument list when the macro is used.\long \global\gdef〈cmd〉〈arg-spec〉{〈text〉}\edef〈cmd〉〈arg-spec〉{〈text〉}\xdef〈cmd〉〈arg-spec〉{〈text〉}If you use the \long qualifier before \def (as \long\def...) then the 〈text〉 andarguments may include paragraphs. The LaTeX version of this is the unstarred\providecommand followed by \renewcommand.To make a command global instead of local to the current group, the \global qualifiercan be used with \def (as \global\def...) when defining it; \gdef is provided as ashorthand for this common case.Normally any macros within the replacement 〈text〉 of a command defined by \def areexpanded when the command is called. The macro \edef also defines a command but inthis case any macros in the replacement 〈text〉 are expanded when the command is defined.Both \long and \global may be used to qualify \edef, and like \gdef being shorthandfor \global\def, \xdef is short for \global\edef.There is much more to the \def family of commands than I have given; consult elsewherefor all the gory details.\let〈cmda〉=〈cmdb〉The \let macro gives 〈cmda〉 the same definition as 〈cmdb〉 at the time the \let is called. The= sign is optional. \let is often used when you want to save the definition of a command.Here is a short example of how some of \def and \let work.\def\name{Alf}\let\fred = \name\name, \fred. % prints Alf, Alf.\def\name{Fred}\name, \fred. % prints Fred, Alf.434