The Define function defines a language for use with CodeGeneration.

f1, f2, ... can be any number of function calls, with the function's name (zeroth operand) being one of AddFunction, AddFunctions, AddOperator, AddPrintHandler, AddType, SetLanguageAttribute.  These function calls accept exactly the same syntax as the Printer functions of the same name.

When ext_lang is provided, the resulting language definition module is identical to the module for language ext_lang, except where the function calls f1, f2, ... override the data of ext_lang.  This provides a convenient mechanism for altering a language in simple ways and testing the result.

Note: In the user-defined procedures added through the function calls f1, f2, ... , it is often necessary to refer to exports of a Printer module, such as Indent, Print, or GetPrecedence.  For correct behavior, every occurrence of these Printer exports within user-defined procedures must be explicitly declared as Printer exports by prefixing them with 'Printer:-', for example, Printer:-Indent, Printer:-Print.  Otherwise, these references will not be properly handled by Define.

$\mathrm{with}\left(\mathrm{CodeGeneration}\right)\:$

LanguageDefinition[Define]("DefineExample", extend = "C",
     SetLanguageAttribute(
           "Indent_Char" = "    ", # use tab character for indentation
           "Indent_Base" = 1,
           "Indent_Increment" = 1
     ),
     AddOperator( Names:-Assignment = ":=" ),
     AddPrintHandler( Names:-Integer =
         proc(x) Printer:-Print( convert(x, 'string') ) end proc
     )
);

$\mathrm{Translate}\left(\sin \left(x\right)\,\mathrm{language}=''DefineExample''\right)$

    cg := sin(x);