问题描述
在下面的程序中
#include< stdio.h>
int main（）
{
int id = 123，io = 0123，ih = 0x123;
long ld = 1234567L，lo = 01234567l，lh = 0X1234567L;
float f = 123.456f;
double d = 01234.56789L;
printf（" id =％d \ t％o \ t％x \ nio =％d \ t％\\\ t％x \ nhh =％d \ t％O \％x \ n"，
id，id，id，io， io，io，ih，ih，ih）;
printf（" ld =％ld \ t％lo \ t％lx \ nlo =％ld \ t％lo \ t％lx \ nlh =％ld \ t％lo \ t％l \ n"，
ld，ld，ld，lo，lo，lo，lh，lh，lh） ;
printf（" f =％lf \ t％le \ t％lg \ n =％lf \ t％lE \ t％lG \ n，f， f，f，d，d，d）;
返回0;
}
输出得到：
id = 123 173 7b
io = 83 123 53
ih = 291％O 123
ld = 1234567 4553207 12d687
lo = 3 42391 1234567 53977
lh = 19088743 110642547 1234567
f = 123.456001 1.234560e + 02 123.456
d = 1234.567890 1.234568E + 03 1234.57
为什么第3行中有％O而不是预期的八进制o / p？
并且对于d而言，最后一个o / p是1234.57。但％g是％lf或％le
对吗？所以如果它是％lf那么为什么它是1234.57而不是1234.56789？
谢谢
in program below
#include <stdio.h>
int main()
{
int id = 123, io = 0123, ih = 0x123;
long ld = 1234567L, lo = 01234567l, lh = 0X1234567L;
float f = 123.456f;
double d = 01234.56789L;
printf("id = %d\t%o\t%x\nio = %d\t%o\t%x\nih = %d\t%O\t%X\n",
id, id, id, io, io, io, ih, ih, ih);
printf("ld = %ld\t%lo\t%lx\nlo = %ld\t%lo\t%lx\nlh = %ld\t%lo\t%l\n",
ld, ld, ld, lo, lo, lo, lh, lh, lh);
printf("f = %lf\t%le\t%lg\nd = %lf\t%lE\t%lG\n", f, f, f, d, d, d);
return 0;
}
the output got is:
id = 123 173 7b
io = 83 123 53
ih = 291 %O 123
ld = 1234567 4553207 12d687
lo = 342391 1234567 53977
lh = 19088743 110642547 1234567
f = 123.456001 1.234560e+02 123.456
d = 1234.567890 1.234568E+03 1234.57
why is there a %O in line 3 instead of octal o/p expected?
and in line for d the last o/p is 1234.57. but %g is either %lf or %le
right? so if it is %lf then why is it 1234.57 instead of 1234.56789?
thanks
推荐答案
八进制输出的格式说明符是％o，而不是％O。在C情况下，
很重要。
The format specifier for octal output is %o, not %O. In C case is
important.
我认为这是一个精确的问题。
I think that''s a precision issue.
因为你把它放在那里。格式字符串的相关片段是
ih =％d \ t％O \ t％X \ n
注意％O in上面的字符串？没有％O转换说明符，
和八进制转换说明符是％o
Because you put it there. The relevant fragment of the format string is
ih = %d\t%O\t%X\n
Notice the %O in the string above? There is no %O conversion specifier,
and the "octal" conversion specifier is %o
谢谢Lew。是否有一个说明符，它会在八进制前面加一个0
数？喜欢0x为％＃x？
thanks Lew. is there a specifier which will put a 0 in front off the octal
number? like 0x for %#x?
0％o怎么样？和0x％x？
[...]
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不要 - 邮寄给我：< mailto：Th ************* @ gmail.com>
What about "0%o" and "0x%x"?
[...]
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Don''t e-mail me at: <mailto:Th*************@gmail.com>
％＃o
C89 4.9.6.1 fprintf功能
＃结果将转换为替代形式。对于o
转换，它会增加精度以强制结果的第一个数字
为零。对于x（或X）转换，
非零结果将以0x（或0X）作为前缀。 [...]
%#o
C89 4.9.6.1 The fprintf Function
# The result is to be converted to an "alternate form." For o
conversion, it increases the precision to force the first digit
of the result to be a zero. For x (or X) conversion, a
nonzero result will have 0x (or 0X) prefixed to it. [...]
C89没有％F（但确实有％E和％G）。 ％E和％G使用
资本E代表指数代号，而不是小写e />
，但分别与％e和％g相同。 br />
-
我们观察到的怪癖和随意性迫使我们得出结论，即我们不是唯一的宇宙。 - Walter Kistler
C89 does not have %F (but does have %E and %G). %E and %G use a
capital E for the exponent signifier instead of a lower-case e
but are otherwise the same as %e and %g respectively.
--
"The quirks and arbitrariness we observe force us to the
conclusion that ours is not the only universe." -- Walter Kistler
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