# Re: storing an integer in a double precision

*From*: glen herrmannsfeldt <gah@xxxxxxxxxxxxxxxx>*Date*: Thu, 5 May 2011 21:30:43 +0000 (UTC)

Lynn McGuire <lmc@xxxxxxxxxx> wrote:

(snip)

Just a lack of understanding of conversion between integers and

double precision on my part. Back when we were primarily single

precision, we had to be very careful, using "ii = xx + 0.1" to

ensure that we did not loose the whole number value of a

incomplete conversion of 12,000 which was stored in the float

as 11.9999.

Well, that is a different question. One hopes that converting

an integer to floating point gives the exact value, and the

conversion back also.

Other than that, there is no guarantee that one gets the exact

value, and many cases where it is unlikely or at least even

odds.

xx = 1./3.

yy = xx * 3

j = yy

Has fairly good odds of not giving 1 for j.

I have noticed lately that I have gotten lazy since we converted

the entire program to double precision and don't add the 0.1

conversion factor anymore as we don't seem to need it anymore.

Not so obvious to me. Though IEEE has some rounding requirements

that others don't, which might increase the odds.

-- glen

.

**References**:**storing an integer in a double precision***From:*Lynn McGuire

**Re: storing an integer in a double precision***From:*Richard Maine

**Re: storing an integer in a double precision***From:*Lynn McGuire

**Re: storing an integer in a double precision***From:*Lynn McGuire

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