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  1. #include <stdio.h>
  2. #include <inttypes.h>
  3.  
  4. #pragma pack(push, 1)
  5. typedef union{
  6.         double     d;
  7.         uint64_t ui;	    
  8. } Unskiloza;
  9. #pragma pack(pop)
  10.  
  11.  
  12. int main() {
  13.   Unskiloza x, y;
  14.   x.d = 40000000000000;
  15.   y.d = 39999999999999;
  16.  
  17.   printf("x.ui =  %#llx\n", x.ui);
  18.   printf("y.ui =  %#llx\n", y.ui);
  19.   printf("(x.ui - y.ui) & mask =  %lld\n", (x.ui-y.ui) & 0x7FFFFFFFFFFFF000L);  // 0
  20.   printf("x.ui - y.ui =  %lld\n", (x.ui-y.ui) );  // 128
  21.   printf("x - y =  %0.2e\n", x.d - y.d);         // 1.00e
  22.   printf( 0== ((x.ui-y.ui) & 0x7FFFFFFFFFFF0000L) ? "is nearly equals" : "not equals at all" );
  23.  
  24.   return 0;
  25. }
Success #stdin #stdout 0s 4508KB
comments (?)
stdin 
Standard input is empty
stdout 
x.ui =  0x42c2309ce5400000
y.ui =  0x42c2309ce53fff80
(x.ui - y.ui) & mask =  0
x.ui - y.ui =  128
x - y =  1.00e+00
is nearly equals
https://ideone.com/wTnBMz
language:
C (gcc 8.3)
created:
6 years ago
visibility:
public

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