Re: Float comparison

Mark McIntyre <markmcintyre@xxxxxxxxxxxxxxxxxxx> writes:
On 22/04/09 02:13, Keith Thompson wrote:

Given:
double x = 1.0;
the value of x is exactly 1.0, no more, no less.

No, you're incorrect there. The value is stored in a representation
which may, or may not, be capable of storing the value 1 exactly, but
the C standard doesn't require it to.

I believe it does. Take a look at C99 5.2.4.2.2, particularly
paragraphs 1 and 2. It defines a (fairly loose parameterized) model
for floating-point types. I think that any floating-point
representation that satisfies that model with the minimum
characteristics given later in that subsection must be able to
represent 1.0 exactly.

[...]

--
Keith Thompson (The_Other_Keith) kst-u@xxxxxxx <http://www.ghoti.net/~kst>
Nokia
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
.

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