to do和doing做主语的区别

ⅰ.动名词和不定式做主语的相同点
1.不定式短语和动名词做主语时，常常为了保持句子的平衡，用it来做形式主语，如：
it
is
not
easy
to
learn
english
well.
it
is
no
use
asking
him
for
help.
2.如果主语用了不定式,表语和宾语也要用不定式;主语用了动名词,表语和宾语也要用动名词,这在英语中称为对称性,如:
to
see
is
to
believe.
=
seeing
is
believing.
(眼见为实)
(85)it
is
better
to
stay
home
than
_a__
out.
a.
to
go
b.
going
c.
go
d.
gone
ⅱ.动名词和不定式做主语的不同点
1.不定式做主语常表示具体的某一动作;表示泛指或一般的抽象的概念时,多用动名词,如:
(92)_b_
is
a
good
form
of
exercise
for
both
young
and
old.
a.
the
walk
b.
walking
c.
to
walk
d.
walk
2.在”there/it
+be+
no
use(good/help/need)”之后常用动名词做主语,而少用不定式,如:
it
/there
is
no
use
crying
over
the
split
milk.
it
/there
is
no
help
taking
this
medicine.
★但是如果该句型中用了for引出不定式的逻辑主语,就只能用不定式,如:
(93)
there
is
no
good
for
us
to
do
that
exercise.
3.不定式可以和when,
where,
how,
what,
whether等连用,在句子中做主语,宾语和表语,而动名词则不能,如:
how
to
solve
the
problem
is
a
hot
potato.
where
to
put
the
box
seems
hard
to
decide.
whether
to
do
it
hasn’t
been
decided.
what
to
do
next
is
up
to
you.
连接上还有许多，可以借鉴

不定式和动名词都可在句子中作主语，一般说来,
有下面几点须给予注意：
(1)
不定式一般表示具体的、特定的行为；而-ing分词一般表示抽象的、一般的行为。如：
To
complete
the
program
needs
much
effort.
完成这项计划需要很大的努力。
Riding
a
bike
can
make
a
man
smart.
骑单车能使一个人敏捷。
(2)
在疑问句中，只能用动名词的复合结构作主语。如：
(3)
在某些句型中通常要用动名词短语作主语。如：It
is
no
use
doing…/
It
is
no
good
doing…
/
It
is
useless
doing…/
It
is
worthwhile
doing…如：
It
is
no
use
talking
your
trouble
to
a
man
like
him.
跟他那样的人谈你的烦恼没有用。
(4)
一般说来，作主语和表语的非谓语动词形式应一致，即：或同时为不定式，或同时为-ing分词。如：
Seeing
is
believing.
眼见为实。
但是，在现代英语中，当表语用来说明主语的特定意义或具体内容时，主语和表语的非谓语动词的形式可以不一致，即，主语用动名词，而表语用动词不定式。如：
Waving
your
hand
is
to
say
“Good-bye”.
挥手就是说“再见”。
Nodding
your
head
is
to
say
“Yes”.
点头就是说“对，是的”。