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(librep.info)Descriptions

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Descriptions
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   In this document the simplest type of descriptions are those defining
variables (Note: Variables), they look something like:

 - Variable: grains-of-sand
     This imaginary variable contains the number of grains of sand in a
     one-mile long stretch of an averagely sandy beach.

   Hooks (Note: Hooks) are also described in this format, the only
difference is that `Variable:' is replaced by `Hook:'.

   Functions (Note: Functions) and macros (Note: Macros) have more
complex descriptions; as well as the name of the object being
described, they also have a list of parameters which the object will
accept. Each parameter in the list is named and may be referred to in
the body of the description.

   Three keyword parameters may also be used: `#!optional', `#!key' and
`#!rest'. They have the same meaning as when used in the lambda-list of
a function definition (Note: Lambda Expressions). That is,
`#!optional' means that all further parameters are optional, and
`#!rest' means that the following parameter actually receives a list of
any unused argument values.

   An example function definition follows.

 - Function: useless-function first `#!optional' second `#!rest' tail
     This function returns a list consisting of the values SECOND (when
     undefined the number 42 is used), all the items in the list TAIL
     and FIRST.

          (useless-function 'foo 'bar 'xyz 20)
              => (bar xyz 20 foo)
          
          (useless-function '50)
              => (42 50)

   Macros and interactive commands are defined in the same way with
`Macro:' or `Command:' replacing `Function:'.

   Special forms (Note: Special Forms) are described similarly to
functions except that the argument list is formatted differently, since
special forms are, by definition, more flexible in how they treat their
arguments. Optional values are enclosed in square brackets
(`[OPTIONAL-ARG]') and three dots (`REPEATED-ARG...') indicate where
zero or more arguments are allowed.