How to get absolute value from double - c-language

Question

I want the absolute-value from a negative double - and I thought the abs-function was as easy to use as in java - but NOT!

It seems that the abs-function returns an int because I have the value 3.8951 and the output is 3.000000

double d1 = abs(-3.8951);
printf("d1: ...%lf", d1);

How can I fix this problem? That is - I want the absolute value of a double.

Did you try `fabs(-3.8951)`? `man abs` says "compute the absolute value of an integer" and `fabs(3)` is cross-referenced in the "SEE ALSO". Never assume that things work the same way across different languages. Especially since Java has classes and can overload methods, but C does not. — lurker, Jan 06 '14 at 18:07
@mbratch - thanks!!!!!!!!!!!!!!! I will consider this in the future — user3155478, Jan 06 '14 at 18:10
abs is only implemented for integer in C. That's why the answers are all recommending you use fabs, which is the floating-point equivalent. — outis nihil, Jan 06 '14 at 18:11
If this question was asked in 2023, it could possibly get -15 downvotes + duplicate + close. :P — Rohan Bari, Jul 30 '23 at 06:19

herohuyongtao · Accepted Answer · 2017-08-12T14:53:45.937

115

Use fabs() (in math.h) to get absolute-value for double:

double d1 = fabs(-3.8951);

edited Aug 12 '17 at 14:53

answered Jan 06 '14 at 18:08

herohuyongtao

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As you where slighty faster than haccks you won. – user3155478 Jan 06 '14 at 18:26
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fabs() is for doubles. fabsf() is for floats. – jigglypuff Sep 07 '16 at 04:36
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Both of them deserve my love equally. – Sipty Nov 22 '17 at 12:16

haccks · Answer 2 · 2017-06-19T18:57:28.083

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Use fabs instead of abs to find absolute value of double (or float) data types. Include the <math.h> header for fabs function.

double d1 = fabs(-3.8951);

edited Jun 19 '17 at 18:57

answered Jan 06 '14 at 18:09

haccks

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score 5 · Answer 3 · answered Jan 06 '14 at 18:11

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It's worth noting that Java can overload a method such as abs so that it works with an integer or a double. In C, overloading doesn't exist, so you need different functions for integer versus double.

answered Jan 06 '14 at 18:11

lurker

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"In C, overloading doesn't exist" --> Disagree in part, research `` to use `fabs()` with various FP types. Similar effect possible. – chux - Reinstate Monica Feb 09 '21 at 17:19

score 0 · Answer 4 · edited Nov 19 '18 at 13:59

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I have found that using cabs(double), cabsf(float), cabsl(long double), __cabsf(float), __cabs(double), __cabsf(long double) is the solution

edited Nov 19 '18 at 13:59

barbsan

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answered Nov 19 '18 at 13:40

Firas Nomaan

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These `cabs`-like functions are for complex numbers, so it may be out of scope of this question. It would be good to [edit] your post and include this information (and maybe explain what's the difference between `cabs` and `__cabs`) – barbsan Nov 19 '18 at 13:58

score 0 · Answer 5 · answered Sep 23 '19 at 22:02

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  //use fabs()
  double sum_primary_diagonal=0;
  double sum_secondary_diagonal=0;
  double difference = fabs(sum_primary_diagonal - sum_secondary_diagonal);

answered Sep 23 '19 at 22:02

Md.Rakibuz Sultan

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How to get absolute value from double - c-language

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