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eintr: Variables

 
 1.7 Variables
 =============
 
 In Emacs Lisp, a symbol can have a value attached to it just as it can
 have a function definition attached to it.  The two are different.  The
 function definition is a set of instructions that a computer will obey.
 A value, on the other hand, is something, such as number or a name, that
 can vary (which is why such a symbol is called a variable).  The value
 of a symbol can be any expression in Lisp, such as a symbol, number,
 list, or string.  A symbol that has a value is often called a
 “variable”.
 
    A symbol can have both a function definition and a value attached to
 it at the same time.  Or it can have just one or the other.  The two are
 separate.  This is somewhat similar to the way the name Cambridge can
 refer to the city in Massachusetts and have some information attached to
 the name as well, such as “great programming center”.
 
    Another way to think about this is to imagine a symbol as being a
 chest of drawers.  The function definition is put in one drawer, the
 value in another, and so on.  What is put in the drawer holding the
 value can be changed without affecting the contents of the drawer
 holding the function definition, and vice versa.
 

Menu

 
· fill-column Example
· Void Function               The error message for a symbol
                                   without a function.
· Void Variable               The error message for a symbol without a value.
 

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