3 definitions
for idempotent
From WordNet (r) 2.0 :
idempotent
adj : unchanged in value following multiplication by itself; "this
matrix is idempotent"
From Jargon File (4.3.1, 29 Jun 2001) :
idempotent adj. [from mathematical techspeak] Acting as if used only
once, even if used multiple times. This term is often used with respect
to C header files, which contain common definitions and declarations
to be included by several source files. If a header file is ever
included twice during the same compilation (perhaps due to nested
#include files), compilation errors can result unless the header file
has protected itself against multiple inclusion; a header file so
protected is said to be idempotent. The term can also be used to
describe an initialization subroutine that is arranged to perform some
critical action exactly once, even if the routine is called several
times.
From The Free On-line Dictionary of Computing (27 SEP 03) :
idempotent
1. A function f : D -> D is idempotent if
f (f x) = f x for all x in D.
I.e. repeated applications have the same effect as one. This
can be extended to functions of more than one argument,
e.g. Boolean & has x & x = x. Any value in the image of an
idempotent function is a fixed point of the function.
2. This term can be used to describe C header files, which
contain common definitions and declarations to be included by
several source files. If a header file is ever included twice
during the same compilation (perhaps due to nested #include
files), compilation errors can result unless the header file
has protected itself against multiple inclusion; a header file
so protected is said to be idempotent.
3. The term can also be used to describe an initialisation
subroutine that is arranged to perform some critical action
exactly once, even if the routine is called several times.
[{Jargon File]
(1995-01-11)
