define与typedef [英] define versus typedef
问题描述
#define和#define之间的区别是什么？和typedef？
A" #define"由预处理器处理并用作名称
substitude而typedef是一个新数据类型的声明
基于现有数据并由编译器处理。
所以，实际上两者都是等价的？或者是否有任何特殊的
案例，它会对使用哪个说明符产生影响？
问候，
克里斯
推荐答案
Christian Christmann写道：
Christian Christmann wrote:
什么是#define与#define之间的区别和typedef？
A" #define由预处理器处理并用作名称
substitude而typedef是基于现有数据类型的新数据类型的声明，由编译器处理。
所以，实际上两者都是等价的？
嗯，你自己在上面回答了这个问题。显然不同的野兽
一共。
或者是否有任何特殊情况会有所不同
使用哪个说明符？
Hi,
what is the difference between a "#define" and typedef?
A "#define" is handled by the preprocessor and serves as a name
substitude whereas "typedef" is a declaration of a new data type
based on an exisiting one and handled by a compiler.
So, actually both things are equivalent?
Well, you answered this yourself above. Obviously different beasts
altogether.
Or are there any special cases where it makes a difference
which specifier is used?
如果有人决定在你整齐的`#define`d new
类型上使用`#undef`，该怎么办？然后`#define将它视为完全不同的东西。在你的下面的一个
`＃include`d文件中。没有告诉你。
`#define`多行类型可能很麻烦（想想`struct`和
`union`）。
我肯定有人会出现并指出其他差异，并且使用`#define`来定义新类型的缺陷。
Christian Christmann写道：
Christian Christmann wrote:
和#define之间的区别是什么？和typedef？
Typedef有一个类型，因此编译器可以强制执行类型检查。
Typedef可以在块或文件中作用域。一旦定义了#define
，它就必须是摆脱它，也就是说，当你没有自动取消时它不会是
留下一个块范围。 #defines可以很多
类型，如float，double，long，char，字符串，代码块等。我是
不确定typedef是否可以一个字符串，它肯定不是一个
宏（代码）。 #defines可以检查定义，typedef不能。
A" #define由预处理器处理并用作名称
substitude而typedef是基于现有数据类型的新数据类型的声明，由编译器处理。
是的。
那么，实际上两者都是等价的吗？或者是否有任何特殊的情况，它会使用哪个说明符？
Hi,
what is the difference between a "#define" and typedef?
Typedef''s have a type thus the compiler can enforce typechecking.
Typedefs can be scoped within blocks or files. Once a #define is
defined it must be undef''d to "get rid of it", that is, it doesn''t
automatically undef when you leave a block scope. #defines can be many
types like float, double, long, char, a string, code blocks, etc. I''m
not sure that a typedef can be a string and it certainly can''t be a
macro (code). #defines can be checked for definedness, typedefs cannot.
A "#define" is handled by the preprocessor and serves as a name
substitude whereas "typedef" is a declaration of a new data type
based on an exisiting one and handled by a compiler.
Yup.
So, actually both things are equivalent? Or are there any special
cases where it makes a difference which specifier is used?
说明符？是的，它有所不同，这取决于你想要什么
。
-
- Mark
Specifier? Yes it makes a difference and it depends on what you want to
do.
--
- Mark
Christian Christmann写道：
Christian Christmann wrote:
" #define"之间的区别是什么？和typedef？
一个是家庭作业问题，另一个是家庭作业问题。
A#define由预处理器处理并用作名称
substitude而typedef是基于现有数据类型的新数据类型的声明，由编译器处理。
有问题吗？答案！答案？问题！
所以，实际上两件事都是等价的？
不是远程的。一个人说声明这个标识符意味着这种类型，
并要求该类型格式正确并在当前范围内引入一个新名称
，所有这意味着加上该名称
可以用作一种类型。另一个说我在哪里写这个名字，假装
我写了这些代币而不是。
或者是否有任何特殊情况会产生影响
说明符？
what is the difference between a "#define" and typedef?
One is a homework question, and the other is a question for homework.
A "#define" is handled by the preprocessor and serves as a name
substitude whereas "typedef" is a declaration of a new data type
based on an exisiting one and handled by a compiler.
Questions? Answers! Answers? Questions!
So, actually both things are equivalent?
Not remotely. One says "declare that this identifier means this type",
and requires that the type is well-formed and introduces a new name
into the current scope, with all that that implies plus that name
can be used as a type. The other says "where I write this name, pretend
I wrote these tokens instead".
Or are there any special cases where it makes a difference which
specifier is used?
[只有其中一个是说明符。]
有很多/一般/它会产生影响的情况。
-
Chris" defined" Dollin
我们没时间找到我们想知道的一切。 /钹的冲突/
[Only one of them is a specifier.]
There are lots of /general/ cases where it makes a difference.
--
Chris "defined" Dollin
"We did not have time to find out everything we wanted to know." /A Clash of Cymbals/
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