后缀允许表达式？ [英] Suffix allowed on expressions?
问题描述
嗨！
表达式是否允许使用后缀？
例如，允许以下内容：
#define SECONDS_PER_YEAR（60 * 60 * 365）UL
我在 http://www.embedded.com/2000/0005/0005feat2.htm
，
但是，在使用这个宏时（或者只是
表达式a =（60 * 60 * 365）UL;），我无法编译。
标准中的哪个位置表示允许/不允许？
听到是否有任何内容也会很有趣测试中的其他问题和答案中的错误。
BRs！
1月2日19:07，dspfun< dsp ... @ hotmail.comwrote：
嗨！
表达式是否允许使用后缀？
例如，允许以下内容：
#define SECONDS_PER_YEAR（60 * 60 * 365）UL
它应该是：
#define SECONDS_PER_YEAR（60 * 60 * 24 * 365）UL
>
我发现这是在C测试中，http：//www.embedded.com/2000/0005/0005feat2.htm
，
然而，我无法在使用时进行编译宏（或只是
表达式a =（60 * 60 * 365）UL;）。
它应该是：
（或只是表达式声明a =（60 * 60 * 24 * 365）UL; ;）
dspfun< ds **** @ hotmail.comwrites：
表达式是否允许使用后缀？
否。你所谈论的后缀只允许在
整数和浮点常数上使用。
例如，允许以下内容：
#define SECONDS_PER_YEAR（60 * 60 * 365）UL
编号为了获得明显的预期效果，你可以写上
#define SECONDS_PER_YEAR（60UL * 60 * 365）
或
#define SECONDS_PER_YEAR（unsigned long int）（60 * 60 * 365）
-
所有代码都应该为了教学目的而刻意写。
如果你的代码不可读，它还没有完成。
- 理查德希思菲尔德
Ben Pfaff< bl*@cs.stanford.eduwrites：
为了得到明显的效果，你可以写
#define SECONDS_PER_YEAR（60UL * 60 * 365）
或
#define SECONDS_PER_YEAR（unsigned long int）（60 * 60 * 365）
哦，为了得到明显的预期价值，你需要
乘以24的额外因子。
-
char a [] =" \ n .CJacehknorstu" ;; int putchar（int）; int main （void）{unsigned long b []
= {0x67dffdff，0x9aa9aa6a，0xa77ffda9,0x7da6aa6a，0xa6 7f6aaa，0xaa9aa9f6,0x11f6}，* p
= b，i = 24; for（; p + =！* p; * p / = 4）switch（0 [p]& 3）case 0：{return 0; for（p - ; i - ; i - ）case +
2：{i ++; if（i）break; else default：continue; if（0）case 1：putchar（a [i& 15]）; break;}}}
Hi!
Are suffixes allowed on expressions?
For example, is the following allowed:
#define SECONDS_PER_YEAR (60 * 60 * 365) UL
I found this in a C test at http://www.embedded.com/2000/0005/0005feat2.htm
,
however, I am not able to compile when using this macro (or just the
expression "a = (60 * 60 * 365) UL;").
Where in the standard does it say that it is allowed/not allowed?
It would also be interesting to hear if there are any faults in the
other questions and answers in the test.
BRs!
On 2 Jan, 19:07, dspfun <dsp...@hotmail.comwrote:Hi!
Are suffixes allowed on expressions?
For example, is the following allowed:
#define SECONDS_PER_YEAR (60 * 60 * 365) ULIt should be:
#define SECONDS_PER_YEAR (60 * 60 * 24 * 365) UL
>
I found this in a C test athttp://www.embedded.com/2000/0005/0005feat2.htm
,
however, I am not able to compile when using this macro (or just the
expression "a = (60 * 60 * 365) UL;").It should be:
(or just the expression statement "a = (60 * 60 * 24 * 365) UL;")
dspfun <ds****@hotmail.comwrites:
Are suffixes allowed on expressions?No. The suffixes that you are talking about are allowed only on
integer and floating-point constants.
For example, is the following allowed:
#define SECONDS_PER_YEAR (60 * 60 * 365) ULNo. To get the apparently intended effect, you can write
#define SECONDS_PER_YEAR (60UL * 60 * 365)
or
#define SECONDS_PER_YEAR (unsigned long int) (60 * 60 * 365)
--
"All code should be deliberately written for the purposes of instruction.
If your code isn''t readable, it isn''t finished yet."
--Richard Heathfield
Ben Pfaff <bl*@cs.stanford.eduwrites:
To get the apparently intended effect, you can write
#define SECONDS_PER_YEAR (60UL * 60 * 365)
or
#define SECONDS_PER_YEAR (unsigned long int) (60 * 60 * 365)Oh, and to get the apparently intended value, you need to
multiply by an additional factor of 24.
--
char a[]="\n .CJacehknorstu";int putchar(int);int main(void){unsigned long b[]
={0x67dffdff,0x9aa9aa6a,0xa77ffda9,0x7da6aa6a,0xa6 7f6aaa,0xaa9aa9f6,0x11f6},*p
=b,i=24;for(;p+=!*p;*p/=4)switch(0[p]&3)case 0:{return 0;for(p--;i--;i--)case+
2:{i++;if(i)break;else default:continue;if(0)case 1:putchar(a[i&15]);break;}}}
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