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Is there any way that i can find wether float variable contains fraction??

 P: n/a Hi Is there any way that i can find wether float variable contains fraction?? for eg:- if( isWholeNumber(b)) { //do here } isWholeNumber(float var) should return true for the float numbers like 10.000 ,11.000 etc and it shuold be false for numbers like 10.112 (if it contains fraction), 11.092123 Jun 18 '07 #1
10 Replies

 P: n/a nas wrote: Hi Is there any way that i can find wether float variable contains fraction?? for eg:- if( isWholeNumber(b)) { //do here } isWholeNumber(float var) should return true for the float numbers like 10.000 ,11.000 etc and it shuold be false for numbers like 10.112 (if it contains fraction), 11.092123 look up fmod() in your favorite reference. Jun 18 '07 #2

 P: n/a On Jun 18, 8:15 am, red floyd

 P: n/a On 2007-06-18 07:52, nas wrote: Hi Is there any way that i can find wether float variable contains fraction?? for eg:- if( isWholeNumber(b)) { //do here } isWholeNumber(float var) should return true for the float numbers like 10.000 ,11.000 etc and it shuold be false for numbers like 10.112 (if it contains fraction), 11.092123 Cast the number to int and back to float/double again and compare. -- Erik Wikström Jun 18 '07 #4

 P: n/a On Jun 18, 2:28 am, Erik Wikström

 P: n/a On 2007-06-18 11:47, nas wrote: On Jun 18, 2:28 am, Erik Wikström On 2007-06-18 07:52, nas wrote: Hi Is there any way that i can find wether float variable contains fraction?? for eg:- if( isWholeNumber(b)) { //do here } isWholeNumber(float var) should return true for the float numbers like 10.000 ,11.000 etc and it shuold be false for numbers like 10.112 (if it contains fraction), 11.092123 Cast the number to int and back to float/double again and compare.--Erik Wikström- Hide quoted text -- Show quoted text - Thanks for all the replies.. This is what i had thought initially(casting to int and back to float)..but my doubt is wether this solution works every time?? i mean..what i think is there will be a probem becoz of truncation.. but i am not able to give the example...do any one have to say about this?? It should work for int and double on a x86 since a double can give an exact representation of all number an int can (so a float and int should also work). This won't work if the number is larger than can be represented by an int (or long or whatever you use) but otherwise I can see no problem (though I'm no expert on floating point numbers). -- Erik Wikström Jun 18 '07 #6

 P: n/a Erik Wikström wrote: Cast the number to int and back to float/double again and compare. That works with float but not with double if the value is too large. Jun 18 '07 #7

 P: n/a James Kanze nas wrote: Is there any way that i can find wether float variable contains fraction?? >look up fmod() in your favorite reference. Interesting. I would have used modf(). (Both will work.) I would have suggested floor() (or possibly ceil() for negative numbers). -- Marcus Kwok Replace 'invalid' with 'net' to reply Jun 19 '07 #8

 P: n/a On Jun 19, 1:05 pm, ricec...@gehennom.invalid (Marcus Kwok) wrote: James Kanze

 P: n/a Guillermo Schwarz wrote: On Jun 19, 1:05 pm, ricec...@gehennom.invalid (Marcus Kwok) wrote: >James Kanze >On Jun 18, 8:15 am, red floyd >>look up fmod() in your favorite reference. >>Interesting. I would have used modf(). (Both will work.) I would have suggested floor() (or possibly ceil() for negativenumbers).--Marcus KwokReplace 'invalid' with 'net' to reply In fact it would be much better to use fractions in the first place, and then if the fraction can't represent the number (for example if it is PI or sqrt(2)) then use float or double. I always thought that PI was 22/7... Isn't that what Archimedes found like, 2500 years ago?... Or was it Pythagoras? I may have had too much coffee, and it's possible that Pi is not a single fraction but rather a whole bunch of them... Fractions never loose precision, so 1/3 * 3 is 1, exactly. Cool. Better than the alternative, right? On my computer std::cout << (1/3 * 3) prints '0'. Jun 19 '07 #10

 P: n/a On 2007-06-19 22:16, Victor Bazarov wrote: Guillermo Schwarz wrote: >On Jun 19, 1:05 pm, ricec...@gehennom.invalid (Marcus Kwok) wrote: >>James Kanze Is there any way that i can find wether float variable contains>fraction??look up fmod() in your favorite reference.Interesting. I would have used modf(). (Both will work.)I would have suggested floor() (or possibly ceil() for negativenumbers).--Marcus KwokReplace 'invalid' with 'net' to reply In fact it would be much better to use fractions in the first place,and then if the fraction can't represent the number (for example if itis PI or sqrt(2)) then use float or double. I always thought that PI was 22/7... Isn't that what Archimedes found like, 2500 years ago?... Or was it Pythagoras? I may have had too much coffee, and it's possible that Pi is not a single fraction but rather a whole bunch of them... No, but 22/7, and even better 355/113, are close enough for most practical purposes. The number is irrational and can not be expressed as a fraction. For better approximations you can download the first few millions of decimals from the net :-) -- Erik Wikström Jun 19 '07 #11