Next: Simple Lambda Up: Lambda Expressions
Components of a Lambda Expression
A function written in Lisp (a "lambda expression") is a list that
looks like this:
The first element of a lambda expression is always the symbol
`lambda'. This indicates that the list represents a function. The
reason functions are defined to start with `lambda' is so that other
lists, intended for other uses, will not accidentally be valid as
The second element is a list of argument variable names (symbols).
This is called the "lambda list". When a Lisp function is called, the
argument values are matched up against the variables in the lambda
list, which are given local bindings with the values provided. *Note
The documentation string is an actual string that serves to describe
the function for the Emacs help facilities. Note: Function
The interactive declaration is a list of the form `(interactive
CODE-STRING)'. This declares how to provide arguments if the function
is used interactively. Functions with this declaration are called
"commands"; they can be called using `M-x' or bound to a key.
Functions not intended to be called in this way should not have
interactive declarations. Note: Defining Commands, for how to write
an interactive declaration.
The rest of the elements are the "body" of the function: the Lisp
code to do the work of the function (or, as a Lisp programmer would say,
"a list of Lisp forms to evaluate"). The value returned by the
function is the value returned by the last element of the body.
automatically generated by info2www