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== Definitions and assignments == TeX's primitive <code>\csname</code> can be used to construct all kind of commands that cannot be defined with <code>\def</code> and <code>\let</code>. Every macro programmer sooner or later wants macros like these. <texcode>\setvalue {name}{...} = \def\name{...}\setgvalue {name}{...} = \gdef\name{...}\setevalue {name}{...} = \edef\name{...}\setxvalue {name}{...} = \xdef\name{...}\letvalue {name}=\... = \let\name=\...\getvalue {name} = \name\resetvalue {name} = \def\name{}</texcode> As we will see, ConTeXt uses these commands many times, which is mainly due to its object oriented and parameter driven character. The next macro can be very useful when using <code>\csname</code> like in: <texcode>\csname if\strippedcsname\something\endcsname</texcode> This expands to <code>\ifsomething</code>. Setups can be optional. A command expecting a setup is prefixed by <code>\complex</code>, a command without one gets the prefix <code>\simple</code>. Commands like this can be defined by: <texcode>\complexorsimple\command</texcode> When <code>\command</code> is followed by a <code>[setup]</code>, then <texcode>\complexcommand [setup]</texcode> executes, else we get <texcode>\simplecommand</texcode> An alternative for <code>\complexorsimple</code> is: <texcode>\complexorsimpleempty {command}</texcode> Depending on the presence of <code>[setup]</code>, this one leads to one of: <texcode>\complexcommando [setup]\complexcommando []<System_Macros/texcode> Many ConTeXt commands started as complex or simple ones, but changed into more versatile (more object oriented) ones using the <code>\get...argument</code> commands later in their existence. The previous commands are used that often that we found it worthwile to offer two more alternatives. These commands are called as: <texcode>\definecomplexorsimple\command</texcode> Of course, we must have available <texcode>\def\complexcommand[#1Definitions_and_Assignments]{...}\def\simplecommand {...}</texcode> Using this construction saves a few strings now and then. We won't go into details here, but the general form of this using this command is: <texcode>\definestartstopcommand\somecommand\e!specifier{arg}{arg}% {do something with arg}</texcode> This expands to something like: <texcode>\def\somecommand arg \startspecifier arg \stopspecifier% {do something with arg}</texcode> The arguments can be anything reasonable, but double <code>#</code>'s are needed in the specification part, like: <texcode>\definestartstopcommand\somecommand\e!specifier{[##1][##2]}{##3}% {do #1 something #2 with #3 arg}</texcode> which becomes: <texcode>\def\somecommand[#1][#2]\startspecifier#3\stopspecifier% {do #1 something #2 with #3 arg}</texcode> Actually, this macro is never used in ConTeXt, but it used to be part of constructions like <code>\placeformula</code>.
→Definitions and assignments
[[System_Macros/Handling_Arguments]]
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