Guide to LaTeX (4th Edition) (Tools and Techniques

H.1. Brief description of the L AT E X commands 535
\DeclareMathVersion{ver} [p] . . . . . . . . . . . . (A.3.3) – 374
Declares ver to be a new math version for math alphabets and
symbol fonts. Initially, the version will use those fonts defined
by \Declare... commands, which may be redefined for this math
version with appropriate \Set... commands.
\DeclareOldFontCommand{\cmd}{text specs}{math specs} [p]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . (A.3.2) – 373
Defines \cmd to be a font declaration that invokes text specs in text
mode, and math specs in math mode. The new command behaves in
math mode as a 2.09 font declaration, although math specs must be
a math font command without its argument. It is meant to define
commands to be compatible with L AT E X 2.09 and should generally be
avoided.
\DeclareOption{option}{code} [p] . . . . . . . . . . . (D.2.3) – 442
In a class or package file, this command defines the set of commands
(code) that is to be associated with the given option. These commands
are executed when \ExecuteOptions or \ProcessOptions is called.
After the latter, all definitions are erased, to save memory. The code
is internally stored in a command named \ds@option.
\DeclareOption*{code} [p] . . . . . . . . . . . . . . . (D.2.3) – 442
In a class or package file, this command defines the default set of
commands that is associated with every undefined option. Special
commands that may be used within code are \CurrentOption (the
name of the option) and \OptionNotUsed. Example:
\DeclareOption*{\InputIfFileExists
{\CurrentOption.sty}{}{\OptionNotUsed}}
\DeclareRobustCommand{\cmd}[narg][opt]{def } . . . (D.2.5) – 445
Defines or redefines the command \cmd in the same way as
\newcommand except that the result is robust: it may be used in
the argument of another command without a \protect command
before it.
\DeclareRobustCommand*{\cmd}[narg][opt]{def } . . (D.2.6) – 445
The same as \DeclareRobustCommand except that the arguments to
\cmd must be ‘short’, not containing any new paragraphs.
\DeclareSymbolFont{sym fnt}{code}{fam}{ser}{shp} [p]
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . (A.3.4) – 374
Declares the math font with the given attributes to be a symbol font
that may be addressed by other commands with the name sym fnt.
The symbol font applies to all math versions unless redefined with a
\SetSymbolFont command.