浮点问题 [英] floating point problem
问题描述
嗨......我遇到了关于浮点的奇怪问题
比较......问题是......
main（）
{
浮动a = 0.7;
if（0.7 a）
printf（" hi"）;
else
printf（" hello"）;
}
i认为答案应该是打招呼...但奇怪的是它很好....但是
a = 0.8答案是你好...再次为a = 0.9答案是嗨.... />
程序在linux系统上运行....如果有人解释这个问题它
将非常有用... thanx提前...再见..
问候，
eric
hi....i have encountered strange problem regarding floating point
comparison...the problem is...
main()
{
float a=0.7;
if(0.7 a)
printf("hi");
else
printf("hello");
}
i think the answer should have hello...but strangely it is hi....but
for a=0.8 the answer is hello...again for a=0.9 the answer is hi....the
program is run on a linux system....if anybody explains this problem it
will be very helpful...thanx in advance...bye..
regards,
eric
推荐答案
< a href =mailto：di ********** @ yahoo.com> di ********** @ yahoo.com 写道：
hi ....我遇到了关于浮点的奇怪问题
比较......问题是......
main（）
{
浮动a = 0.7;
if（0.7 a）
printf（" hi"）;
else
printf（" hello"）;
}
i认为答案应该有问好......但奇怪的是它是嗨....但是
a = 0.8答案是你好...再次a = 0.9答案是嗨....
程序是在linux系统上运行的。 ...如果有人解释这个问题它
将非常有帮助... ...提前...再见...
hi....i have encountered strange problem regarding floating point
comparison...the problem is...
main()
{
float a=0.7;
if(0.7 a)
printf("hi");
else
printf("hello");
}
i think the answer should have hello...but strangely it is hi....but
for a=0.8 the answer is hello...again for a=0.9 the answer is hi....the
program is run on a linux system....if anybody explains this problem it
will be very helpful...thanx in advance...bye..
欢迎到了浮点的欢乐，不精确的世界。请参阅
组的常见问题解答，所有内容都将被解释。
-
Ian Collins。
Welcome to the joyous, imprecise world of floating point. Consult the
group''s FAQ and all will be explained.
--
Ian Collins.
di ********** @ yahoo.com 写道：
hi ....我遇到了关于浮点的奇怪问题
比较..问题是......
main（）
{
浮动a = 0.7;
if（0.7 a）
printf（" hi"）;
else
printf（" hello"）;
}
i认为答案应该有问好......但奇怪的是它是嗨....但是
a = 0.8你好答案是...你好...... = 0.9答案是嗨....
程序在linux系统上运行....如果有人解释这个问题它
将非常有帮助... ...提前感谢...再见..
hi....i have encountered strange problem regarding floating point
comparison...the problem is...
main()
{
float a=0.7;
if(0.7 a)
printf("hi");
else
printf("hello");
}
i think the answer should have hello...but strangely it is hi....but
for a=0.8 the answer is hello...again for a=0.9 the answer is hi....the
program is run on a linux system....if anybody explains this problem it
will be very helpful...thanx in advance...bye..
我得不到相同的结果。它确实说嗨对于第一个，但是
是你好对于第二和第三个案件。这是你的意思吗？
I don''t get the same results. It does say "hi" for the first one, but
is "hello" for the second and third cases. Is this what you meant?
> hi ....我遇到了关于浮点的奇怪问题
>hi....i have encountered strange problem regarding floating point
>比较......问题是......
>comparison...the problem is...
中没有大多数非整数值的确切表示
二进制浮点数。最接近的可能值可能高于或低于确切数学值的b $ b。
0.7为双倍：
之前：0.699999999999999844568776552478084340691566467285 156250000000
价值：0.699999999999999955591079014993738383054733276367 187500000000
后：0.700000000000000066613381477509392425417900085449 218750000000
0.7浮动：
之前： 0.699999928474426269531250000000000000000000000000 000000000000
价值：0.699999988079071044921875000000000000000000000000 000000000000
后：0.700000047683715820312500000000000000000000000000 000000000000
0.8双倍：
之前：0.799999999999999933386618522490607574582099914550 781250000000
价值：0.800000000000000044408920985006261616945266723632 812500000000
之后：0.800000000000000155431223447521915659308433532714 843750 000000
0.8浮动：
之前：0.799999952316284179687500000000000000000000000000 000000000000
价值：0.800000011920928955078125000000000000000000000000 000000000000
之后：0.800000071525573730468750000000000000000000000000 000000000000
There is no exact representation for most non-integer values in
binary floating point. The closest possible value may be above or
below the exact mathematical value.
0.7 as double:
Before: 0.699999999999999844568776552478084340691566467285 156250000000
Value: 0.699999999999999955591079014993738383054733276367 187500000000
After: 0.700000000000000066613381477509392425417900085449 218750000000
0.7 as float:
Before: 0.699999928474426269531250000000000000000000000000 000000000000
Value: 0.699999988079071044921875000000000000000000000000 000000000000
After: 0.700000047683715820312500000000000000000000000000 000000000000
0.8 as double:
Before: 0.799999999999999933386618522490607574582099914550 781250000000
Value: 0.800000000000000044408920985006261616945266723632 812500000000
After: 0.800000000000000155431223447521915659308433532714 843750000000
0.8 as float:
Before: 0.799999952316284179687500000000000000000000000000 000000000000
Value: 0.800000011920928955078125000000000000000000000000 000000000000
After: 0.800000071525573730468750000000000000000000000000 000000000000
>
main（）
浮动a = 0.7;
if（0.7 a）
printf（" hi"）;
else
printf（" hello"）;
}
我认为答案应该是你好......但奇怪的是它是嗨...但是对于a = 0.8
答案是你好...再次a = 0.9答案是嗨.....
程序在linux系统上运行....如果有人解释这个问题它将非常有用...而且提前...再见..
>
main()
{
float a=0.7;
if(0.7 a)
printf("hi");
else
printf("hello");
}
i think the answer should have hello...but strangely it is hi....but
for a=0.8 the answer is hello...again for a=0.9 the answer is hi....the
program is run on a linux system....if anybody explains this problem it
will be very helpful...thanx in advance...bye..
Gordon L. Burditt
Gordon L. Burditt
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