question on variable type "double"

Question

i have written a program and it works with 3D coordinates (i.e. x,y,z).

input data for my program was like

50903.85 21274.97 15.03 
50903.57 21274.96 15.08 
50903.33 21274.95 15.17

and i got the output with some more columns. So, i got the same x,y,z for my output file.

50903.85 21274.97 15.03 
50903.57 21274.96 15.08 
50903.33 21274.95 15.17

so, my program works properly, i guess.

then, i used another data set, having more digits than the previous data,

512330.98 5403752.71 330.39 
512331.01 5403754.18 329.44 
512331.06 5403755.59 329.56

and my output was like;

512331 5.40375e+006 330.39 
512331 5.40375e+006 329.44 
512331 5.40376e+006 329.56

here, i am not able to get real values. and x values are also rounded. i cant think what should be the reason?

in my program, i used "double" for assigning variables for x,y,z values. SO, i would like to know what is the maximum numerical value that can be refereed to double?

if someone need to work with very long values, what should be the relevant variable?

Check out this page: http://www.cplusplus.com/reference/iostream/manipulators/setprecision/ and this one: http://www.cplusplus.com/reference/iostream/manipulators/scientific/ — Thomas Matthews, Mar 03 '11 at 23:45

score 1 · Answer 1 · answered Mar 03 '11 at 23:41

1

Those numbers, such as 5.40375e+006, are another way of representing doubles. When they get sufficiently large, they are by default printed in scientific notation. 5.40375e+006 is 5.40375 * 10^6, or 5403750.

answered Mar 03 '11 at 23:41

dappawit

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score 1 · Accepted Answer · edited May 23 '17 at 09:58

1

Numbers aren't changing, you are just seeing a different notation change there. Perhaps you are using something other than %f to format your doubles? See printf format parameters.

Better yet, check out this StackOverflow question: How to avoid scientific notation for large numbers?

edited May 23 '17 at 09:58

Community

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answered Mar 03 '11 at 23:42

Julio Gorgé

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thanks, i found a simple way from there. write_roof.setf(ios::fixed); – niro Mar 04 '11 at 00:07

score 0 · Answer 3 · answered Mar 03 '11 at 23:43

0

Have a look at this http://www.cplusplus.com/reference/clibrary/cfloat/

answered Mar 03 '11 at 23:43

Morten Kristensen

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score 0 · Answer 4 · answered Mar 03 '11 at 23:46

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Doubles have about 16 decimals of accuracy (source), so you shouldn't have any problem here, unless you're printing floats.

answered Mar 03 '11 at 23:46

tugudum

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question on variable type "double"

4 Answers4