cl: Function Bindings
4.3.2 Function Bindings
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These forms make ‘let’-like bindings to functions instead of variables.
-- Macro: cl-flet (bindings...) forms...
This form establishes ‘let’-style bindings on the function cells of
symbols rather than on the value cells. Each BINDING must be a
list of the form ‘(NAME ARGLIST FORMS...)’, which defines a
function exactly as if it were a ‘cl-defun’ form. The function
NAME is defined accordingly but only within the body of the
‘cl-flet’, hiding any external definition if applicable.
The bindings are lexical in scope. This means that all references
to the named functions must appear physically within the body of
the ‘cl-flet’ form.
Functions defined by ‘cl-flet’ may use the full Common Lisp
argument notation supported by ‘cl-defun’; also, the function body
is enclosed in an implicit block as if by ‘cl-defun’. 
Program Structure.
Note that the ‘cl.el’ version of this macro behaves slightly
differently. In particular, its binding is dynamic rather than
lexical. Obsolete Macros.
-- Macro: cl-labels (bindings...) forms...
The ‘cl-labels’ form is like ‘cl-flet’, except that the function
bindings can be recursive. The scoping is lexical, but you can
only capture functions in closures if ‘lexical-binding’ is ‘t’.
(elisp)Closures, and (elisp)Using Lexical Binding.
Lexical scoping means that all references to the named functions
must appear physically within the body of the ‘cl-labels’ form.
References may appear both in the body FORMS of ‘cl-labels’ itself,
and in the bodies of the functions themselves. Thus, ‘cl-labels’
can define local recursive functions, or mutually-recursive sets of
functions.
A “reference” to a function name is either a call to that function,
or a use of its name quoted by ‘quote’ or ‘function’ to be passed
on to, say, ‘mapcar’.
Note that the ‘cl.el’ version of this macro behaves slightly
differently. Obsolete Macros.
Info Catalog
cl: Dynamic Bindings
cl: Variable Bindings
cl: Macro Bindings