How to Convert double to int in C

Question

double a  a   3669 0  int b  b   a    I am getting 3668 in b  instead of 3669   How do I fix This problem   And if have 3559 8 like that also I want like 3559 not 3560

User · Answer

I suspect you don t actually have that problem - I suspect you ve really got   double a   callSomeFunction       Examine a in the debugger or via logging  and decide it s 3669 0     Now cast int b    int  a     Now a is 3668   What makes me say that is that although it s true that many decimal values cannot be stored exactly in float or double  that doesn t hold for integers of this kind of magnitude  They can very easily be exactly represented in binary floating point form   Very large integers can t always be exactly represented  but we re not dealing with a very large integer here    I strongly suspect that your double value is actually slightly less than 3669 0  but it s being displayed to you as 3669 0 by whatever diagnostic device you re using  The conversion to an integer value just performs truncation  not rounding - hence the issue   Assuming your double type is an IEEE-754 64-bit type  the largest value which is less than 3669 0 is exactly  3668 99999999999954525264911353588104248046875   So if you re using any diagnostic approach where that value would be shown as 3669 0  then it s quite possible  probable  I d say  that this is what s happening

User · Answer

This is the notorious floating point rounding issue  Just add a very small number  to correct the issue   double a  a 3669 0  int b  b a  1e-9

User · Answer

int b  double a  a 3669 0  b a  printf  b  d  b     this code gives the output as b 3669 only you check it clearly

User · Answer

main         double a      a 3669 0      int b      b a      printf  quot b is  d quot  b         output is  b is 3669 when you write b a  then its automatically converted in int see on-line compiler result     http   ideone com 60T5b  This is called Implicit Type Conversion Read more here https   www geeksforgeeks org implicit-type-conversion-in-c-with-examples

[c] How to Convert double to int in C?

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