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16.5.3 Functions in Typed Languages

The @deftypefn command and its variations are for describing functions in languages in which you must declare types of variables and functions, such as C and C++.

@deftypefn category data-type name arguments

The @deftypefn command is the general definition command for functions and similar entities that may take arguments and that are typed. The @deftypefn command is written at the beginning of a line and is followed on the same line by the category of entity being described, the type of the returned value, the name of this particular entity, and its arguments, if any.

For example,

@deftypefn {Library Function} int foobar @
  (int @var{foo}, float @var{bar})
@end deftypefn


Library Function: int foobar (int foo, float bar)

This means that foobar is a “library function” that returns an int, and its arguments are foo (an int) and bar (a float).

Since in typed languages, the actual names of the arguments are typically scattered among data type names and keywords, Texinfo cannot find them without help. You can either (a) write everything as straight text, and it will be printed in slanted type; (b) use @var for the variable names, which will uppercase the variable names in Info and use the slanted typewriter font in printed output; (c) use @var for the variable names and @code for the type names and keywords, which will be dutifully obeyed.

The template for @deftypefn is:

@deftypefn category data-type name argumentsbody-of-description
@end deftypefn

Note that if the category or data type is more than one word then it must be enclosed in braces to make it a single argument.

If you are describing a procedure in a language that has packages, such as Ada, you might consider using @deftypefn in a manner somewhat contrary to the convention described in the preceding paragraphs. For example:

@deftypefn stacks private push @
       (@var{s}:in out stack; @
       @var{n}:in integer)
@end deftypefn

(In these examples the @deftypefn arguments are shown using continuations (see section Definition Command Continuation Lines), but could be on a single line.)

In this instance, the procedure is classified as belonging to the package stacks rather than classified as a ‘procedure’ and its data type is described as private. (The name of the procedure is push, and its arguments are s and n.)

@deftypefn creates an entry in the index of functions for name.

@deftypefun data-type name arguments

The @deftypefun command is the specialized definition command for functions in typed languages. The command is equivalent to ‘@deftypefn Function …’. The template is:

@deftypefun type name argumentsbody-of-description
@end deftypefun

@deftypefun creates an entry in the index of functions for name.

Ordinarily, the return type is printed on the same line as the function name and arguments, as shown above. In source code, GNU style is to put the return type on a line by itself. So Texinfo provides an option to do that: @deftypefnnewline on.

This affects typed functions only—not untyped functions, not typed variables, etc.. Specifically, it affects the commands in this section, and the analogous commands for object-oriented languages, namely @deftypeop and @deftypemethod (see section Object-Oriented Methods).

Specifying @deftypefnnewline off reverts to the default.

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