STL地图问题 [英] STL map question
问题描述
大家好，
首先，我知道我的问题与STL有关。
但是comp.std.c ++组经过审核，我不知道要花多长时间才能在那里回答。所以，请你着火。
现在的问题是：
是否有任何特殊原因（性能等）使用"（* i）.second"
而不是i-> second？
示例如下：
typedef std :: map< ...>表;
extern table t;
table :: iterator i;
for（i = t.begin（）; i！= t.end（）; i ++）
{
param =（* i）.second;
...
}
谢谢。
Hello all,
First of all I am aware of the fact that my question is STL related.
However the comp.std.c++ group is moderated and I have no idea how long
it will take to be answered there. So, please, hold your fire.
And now the question:
Is there any special reason (performance, etc.) for using "(*i).second"
instead of "i->second"?
The example follows:
typedef std::map<...> table;
extern table t;
table::iterator i;
for (i=t.begin(); i!=t.end(); i++)
{
param = (*i).second;
...
}
Thanks.
推荐答案
" brian" <峰; br *********** @ yahoo.com>在消息中写道
news：11 ********************** @ z14g2000cwz.googlegr oups.com ...
"brian" <br***********@yahoo.com> wrote in message
news:11**********************@z14g2000cwz.googlegr oups.com...
首先，我知道我的问题与STL有关。
然而comp.std.c ++组被审核，我不知道它将需要多长时间在那里回答。所以，请你举起火来。
欢迎所有C ++问题，没有预料之火。
是否有任何特殊原因（性能等）使用（* i）.second
而不是i-> second？
First of all I am aware of the fact that my question is STL related.
However the comp.std.c++ group is moderated and I have no idea how long
it will take to be answered there. So, please, hold your fire. All C++ questions are welcome here, no fire to be expected.
Is there any special reason (performance, etc.) for using "(*i).second"
instead of "i->second"?
不，绝对不是。
6到7年前的b $ b，有些人说的是（*一世）。可能更便携
即i-> ，由于某些库
实现的不一致 - 但这是历史。
我认为今天没有理由选择（* i）。在i->
hth-Ivan
-
http://ivan.vecerina.com/contact/?subject=NG_POST < - 电子邮件联系表格
No, most certainly not.
6-7 years ago, some were saying that (*i). may be more portable
that i-> , because of the inconsistency of some library
implementations - but this is history.
I see no rationale today for preferring (*i). over i->
hth-Ivan
--
http://ivan.vecerina.com/contact/?subject=NG_POST <- email contact form
brian写道：
大家好，
首先，我知道我的问题与STL有关。
然而comp。 std.c ++小组是主持的，我不知道如何在那里回答它需要多长时间。请你好好开火。
现在的问题是：
是否有任何特殊原因（表现等）使用
（* ⅰ）。第二"而不是i->秒？
不，只是个人喜好。
示例如下：
typedef std :: map< ...> table;
extern table t;
table :: iterator i;
for（i = t.begin（）; i！= t.end（）; i ++）
Hello all,
First of all I am aware of the fact that my question is STL related.
However the comp.std.c++ group is moderated and I have no idea how
long it will take to be answered there. So, please, hold your fire.
And now the question:
Is there any special reason (performance, etc.) for using
"(*i).second" instead of "i->second"?
No, just personal preference.
The example follows:
typedef std::map<...> table;
extern table t;
table::iterator i;
for (i=t.begin(); i!=t.end(); i++)
但是这里使用post增量会有性能上升。尽可能使用++ i
。
Jeff Flinn
But there is a performance hit here using post increment. Use ++i instead
whenever possible.
Jeff Flinn
2月18日星期五2005 13:18:24 +0100，Ivan Vecerina
< NO **************************** ******@vecerina.com>写道：
On Fri, 18 Feb 2005 13:18:24 +0100, Ivan Vecerina
<NO**********************************@vecerina.com > wrote:
" brian" <峰; br *********** @ yahoo.com>在消息中写道
新闻：11 ********************** @ z14g2000cwz.googlegr oups.com ...
"brian" <br***********@yahoo.com> wrote in message
news:11**********************@z14g2000cwz.googlegr oups.com...
首先，我知道我的问题与STL有关。
然而comp.std.c ++组被审核，我不知道在那里需要多长时间才能得到回答。那么，请你好好开火。
First of all I am aware of the fact that my question is STL related.
However the comp.std.c++ group is moderated and I have no idea how long
it will take to be answered there. So, please, hold your fire.
欢迎所有C ++问题，没有预料之火。
All C++ questions are welcome here, no fire to be expected.
是否有任何特殊原因（性能等） 。）使用（* i）.second
而不是i-> second？
Is there any special reason (performance, etc.) for using "(*i).second"
instead of "i->second"?
不，绝对不是。
6-7岁有人说（* i）。可能更便携
i-> ，由于某些库实现的不一致 - 但这是历史。
我认为今天没有理由选择（* i）。在i->
No, most certainly not.
6-7 years ago, some were saying that (*i). may be more portable
that i-> , because of the inconsistency of some library
implementations - but this is history.
I see no rationale today for preferring (*i). over i->
啊，谢谢，我也记得听到过这个但不是为什么，我用了
- >在我的所有C ++代码中形成多年没有问题。
Chris C
Ah, thanks, I too remembered hearing about it but not why, I''ve used the
-> form in all of my C++ code for many years with no problems.
Chris C
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