CODEWITHSUNDEEP
c++cfloating-pointprecision
FidelCashflo
FidelCashflo

Reputation: 533

C - Printing out float values

I have a C++ program that takes in values and prints out values like this:

getline(in,number);
cout << setw(10) << number << endl;

I have an equivalent C program that takes in values and prints out like so:

fscanf(rhs, "%e", &number);
printf("%lf\n", number);

But while the C++ program prints out, 0.30951 the C program prints out 0.309510. More examples: C++: 0.0956439 C: 0.095644. It seems to print the same results as long as the value is 7 digits long, but if its shorter the 7 digits, it adds an extra 0 at the end. And if its longer than 7 digits, it rounds down to 6 digits. I would like the C results to match the C++ program. Any help would be appreciated.

Thanks.

Note: number is a float and number are read from a file.

Upvotes: 10

Views: 87434

Answers (3)

Sava Vranešević
Sava Vranešević

Reputation: 301

printf("%g\n", number);

Will solve your problem, %lf is used for double, %f is used for float, and %g is used for float when you want to display all the decimal places and cut off zeros.

Upvotes: 6

Bob Kaufman
Bob Kaufman

Reputation: 12815

Take advantage of the length and precision specifiers in C formatted print statements:

printf( "%6.4lf", number );

Prints four decimal places in a "cell" six characters wide.

You can use a wildcard character for either length or precision to provide that value at runtime:

int precision = 4;

printf( "%6.*lf", precision, number );

Upvotes: 14

Alex Chamberlain
Alex Chamberlain

Reputation: 4207

Take advantage of the length and precision specifiers in C++ iostreams

std::cout.precision(4);
std::cout << std::setw(10) << number << "\n";

Upvotes: 14

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