monad 音标拼音: [m'onæd]
n . 单位,单一体,单细胞生物
单位,单一体,单细胞生物
monad 一元
monad n 1 : (
chemistry )
an atom having a valence of one 2 :
a singular metaphysical entity from which material properties are said to derive [
synonym : {
monad }, {
monas }]
3 : (
biology )
a single -
celled microorganism (
especially a flagellate protozoan )
Monad \
Mon "
ad \,
n . [
L .
monas , -
adis ,
a unit ,
Gr . ?, ?,
fr .
mo `
nos alone .]
1 .
An ultimate atom ,
or simple ,
unextended point ;
something ultimate and indivisible .
[
1913 Webster ]
2 . (
Philos .
of Leibnitz )
The elementary and indestructible units which were conceived of as endowed with the power to produce all the changes they undergo ,
and thus determine all physical and spiritual phenomena .
[
1913 Webster ]
3 . (
Zool .)
One of the smallest flagellate Infusoria ;
esp .,
the species of the genus {
Monas },
and allied genera .
[
1913 Webster ]
4 . (
Biol .)
A simple ,
minute organism ;
a primary cell ,
germ ,
or plastid .
[
1913 Webster ]
5 . (
Chem .)
An atom or radical whose valence is one ,
or which can combine with ,
be replaced by ,
or exchanged for ,
one atom of hydrogen .
[
1913 Webster ]
{
Monad deme } (
Biol .),
in tectology ,
a unit of the first order of individuality .
[
1913 Webster ]
63 Moby Thesaurus words for "
monad ":
I ,
ace ,
air ,
an existence ,
atom ,
atomic particles ,
being ,
body ,
brute matter ,
building block ,
chemical element ,
component ,
constituent ,
creature ,
critter ,
earth ,
electron ,
element ,
elementary particle ,
elementary unit ,
entelechy ,
entity ,
fire ,
fundamental particle ,
hyle ,
hypostasis ,
individual ,
ion ,
life ,
material ,
material world ,
materiality ,
matter ,
meson ,
molecule ,
natural world ,
nature ,
no other ,
none else ,
nothing else ,
nought beside ,
nuclear particle ,
object ,
one ,
one and only ,
organism ,
person ,
persona ,
personality ,
physical world ,
plenum ,
proton ,
quark ,
something ,
soul ,
stuff ,
substance ,
substratum ,
the four elements ,
thing ,
unit ,
unit of being ,
water /mo 'nad / A technique from
category theory } which has been adopted as a way of dealing
with {state } in {functional programming languages } in such a
way that the details of the state are hidden or abstracted out
of code that merely passes it on unchanged .
A monad has three components : a means of augmenting an
existing type , a means of creating a default value of this new
type from a value of the original type , and a replacement for
the basic application operator for the old type that works
with the new type .
The alternative to passing state via a monad is to add an
extra argument and return value to many functions which have
no interest in that state . Monads can encapsulate state , side
effects , exception handling , global data , etc . in a purely
lazily functional way .
A monad can be expressed as the triple , (M , unitM , bindM )
where M is a function on types and (using {Haskell } notation ):
unitM :: a -> M a
bindM :: M a -> (a -> M b ) -> M b
I .e . unitM converts an ordinary value of type a in to monadic
form and bindM applies a function to a monadic value after
de -monadising it . E .g . a state transformer monad :
type S a = State -> (a , State )
unitS a = \ s0 -> (a , s0 )
m `bindS ` k = \ s0 -> let (a ,s1 ) = m s0
in k a s1
Here unitS adds some initial state to an ordinary value and
bindS applies function k to a value m . (`fun ` is Haskell
notation for using a function as an {infix } operator ). Both m
and k take a state as input and return a new state as part of
their output . The construction
m `bindS ` k
composes these two state transformers into one while also
passing the value of m to k .
Monads are a powerful tool in {functional programming }. If a
program is written using a monad to pass around a variable
like the state in the example above ) then it is easy to
change what is passed around simply by changing the monad .
Only the parts of the program which deal directly with the
quantity concerned need be altered , parts which merely pass it
on unchanged will stay the same .
In functional programming , unitM is often called initM or
returnM and bindM is called thenM . A third function , mapM is
frequently defined in terms of then and return . This applies
a given function to a list of monadic values , threading some
variable (e .g . state ) through the applications :
mapM :: (a -> M b ) -> [a ] -> M [b ]
mapM f [] = returnM []
mapM f (x :xs ) = f x `thenM ` ( \ x2 ->
mapM f xs `thenM ` ( \ xs2 ->
returnM (x2 : xs2 ) ))
2000 -03 -09 )
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