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  1. #include <iostream>
  2. #include <iomanip>
  3. #include <sstream>
  4.  
  5. int main() {
  6. 	std::string data = "3.236568949";
  7.     std::stringstream ss(data);
  8.     long double ld;
  9.     ss >> ld;
  10.  
  11.     std::cout << "Size (in bytes) of a double: " << sizeof(double)
  12.               << " while a long double: " << sizeof(long double) << '\n'
  13.               << "Original string: " << data << '\n'
  14.               << "Converted number:\n" << std::setprecision(10) << ld << '\n'
  15.               << "Same number, but with more outputted decimal figures:\n"
  16.               << std::setprecision(100) << ld << '\n';
  17.  
  18.     std::cout << "\nNow let's try to limit the precision.\n";
  19.  
  20.     std::stringstream ss2;
  21.     long double ld2;
  22.     ss2 << std::setprecision(4) << ld;
  23. 	ss2 >> ld2;
  24.     std::cout << "Converted number:\n" << std::setprecision(10) << ld2 << '\n'
  25.               << "Same number, but with more outputted decimal figures:\n"
  26.               << std::setprecision(100) << ld2 << '\n';
  27.  
  28. 	return 0;
  29. }
Success #stdin #stdout 0s 15240KB
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stdin
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Standard input is empty
stdout
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Size (in bytes) of a double: 8 while a long double: 16
Original string: 3.236568949
Converted number:
3.236568949
Same number, but with more outputted decimal figures:
3.23656894899999999994262556146651377275702543556690216064453125

Now let's try to limit the precision.
Converted number:
3.237
Same number, but with more outputted decimal figures:
3.23699999999999999994622357224471898007323034107685089111328125
https://ideone.com/9w8srR
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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