丢失精度分配浮点值？ [英] Loss of precision assigning floating point values?

问题描述

如何检查浮点数到双精度（反之亦然）

是否会导致精度损失？

解决方案

BigMan写道：

如何判断浮点数为double（反之亦然）
是否会导致精度损失？

将float赋值给double总是精确的。将

a double分配给一个浮点数会导致精度损失，如果双尾数在其尾数部分超出
的范围内有非零位数。浮动的
尾数。没有平台无关的支票

你可以做，这一切都取决于浮动的表示和

双重类型。


V

Victor Bazarov写道：

BigMan写道：

如何检查float的赋值是否为double（或者反$ b $反之亦然）会导致精度损失？

将float赋值给double总是精确的。如果double在其尾部的部分中具有超过浮点数的尾数大小的非零位，则将双精度分配给浮点将导致精度损失。没有平台无关的检查，你可以做，这一切都取决于浮动和
双重类型的表示。

V

double d = ...;

float f =（float）d;

bool loss =（d！=（double）f ）;


？


问候，

Bogdan Sintoma

Bogdan Sintoma写道：

Victor Bazarov写道：

BigMan写道：

我怎样才能检查是否将浮点数赋值为double（或者反之亦然）
会导致精度损失？

将浮点数分配给双精灵总是精确的。如果double在其尾部的部分中具有超过浮点数的尾数大小的非零位，则将双精度分配给浮点将导致精度损失。没有平台无关的检查，你可以做，这一切都取决于浮动和
双重类型的表示。

V

double d = ...;
float f =（float）d;
bool loss =（d！=（double）f）;

？

我认为这可以衡量如果分配_has_resulted_失去了

精度，而不是它_will_结果，你不同意吗？


V

How can I check if assignment of a float to a double (or vice versa)
will result in loss of precision?

解决方案

BigMan wrote:

How can I check if assignment of a float to a double (or vice versa)
will result in loss of precision?

Assignment of a float to a double is always precise. Assignment of
a double to a float will cause loss of precision if the double has
non-zero bits in the part of its mantissa beyond the size of the
mantissa of the float. There is no platform-independent check that
you could do, it all depends on the representation of the float and
double types.

V

Victor Bazarov wrote:

BigMan wrote:

How can I check if assignment of a float to a double (or vice versa) will result in loss of precision?

Assignment of a float to a double is always precise. Assignment of
a double to a float will cause loss of precision if the double has
non-zero bits in the part of its mantissa beyond the size of the
mantissa of the float. There is no platform-independent check that
you could do, it all depends on the representation of the float and
double types.

V

double d = ...;
float f = (float)d;
bool loss = (d != (double)f);

?

Regards,
Bogdan Sintoma

Bogdan Sintoma wrote:

Victor Bazarov wrote:

BigMan wrote:

How can I check if assignment of a float to a double (or vice
versa)
will result in loss of precision?

Assignment of a float to a double is always precise. Assignment of
a double to a float will cause loss of precision if the double has
non-zero bits in the part of its mantissa beyond the size of the
mantissa of the float. There is no platform-independent check that
you could do, it all depends on the representation of the float and
double types.

V

double d = ...;
float f = (float)d;
bool loss = (d != (double)f);

?

I think this measures if the assignment _has_resulted_ in a loss of
precision, not if it _will_ result, don''t you agree?

V

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