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QuestionMFC Grid control 2.27 Pin
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QuestionWhen should printf round a floating number up for display? Pin
Member 419459328-Dec-12 5:11
memberMember 419459328-Dec-12 5:11 
Specifically this statement:
printf("Chi square distribution for %s samples is %1.2f (%1.4f), and randomly\n",
   String_Value, chisq, chisq);

I re-implemented this program in MASM to speed it up and I get the following difference (note that I added the (%1.4f)) to display the pre-rounded number to see why I was getting differences:

------------------------------------------------------------------ 17
Chi square distribution for 2048 samples is 6.13 (6.1250), and randomly
-------------------------------------------------------------- 17
Chi square distribution for 2048 samples is 6.12 (6.1250), and randomly

The question is, which one is correct according to the C spec? Should 6.1250 round up to 6.13 or should it take 6.1250+ to round up?

There are other questions such as the following:
printf("of this %s %s file by %d (%2.2f) percent.\n\n", String_Value, samp,
   (short) (((100 * ((binary ? 1 : 8) - ent) / (binary ? 1.0 : 8.0)) + 0.5)),
            ((100 * ((binary ? 1 : 8) - ent) / (binary ? 1.0 : 8.0))));

The cast to a (short) seems to truncate a 5.7 to 5, I had to add the (.... + 0.5) just before the cast in order to get the rounded number. Again, I added the (%2.2f) to display the rounding differences.

Which is correct according to the C spec, rounding or truncation?

The program being re implemented is John Walker's ENT.

Dave.
AnswerRe: When should printf round a floating number up for display? Pin
Richard MacCutchan28-Dec-12 5:53
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GeneralRe: When should printf round a floating number up for display? Pin
Member 419459328-Dec-12 6:55
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GeneralRe: When should printf round a floating number up for display? Pin
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GeneralRe: When should printf round a floating number up for display? Pin
Member 419459328-Dec-12 7:08
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GeneralRe: When should printf round a floating number up for display? Pin
Richard MacCutchan28-Dec-12 7:18
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GeneralRe: When should printf round a floating number up for display? Pin
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GeneralRe: When should printf round a floating number up for display? Pin
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GeneralRe: When should printf round a floating number up for display? Pin
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AnswerRe: When should printf round a floating number up for display? Pin
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Questiongraphics.h multi-threading problem Pin
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