CODEWITHSUNDEEP
c++printfdoublecout
Youssef13
Youssef13

Reputation: 4954

cout prints inaccurate result and printf prints accurate result

The following code in C++:

    double x = 500000.6;
    printf("%f\n", x);
    cout << x << endl;

prints the following:

500000.600000
500001

Why cout isn't printing the correct value (500000.6)?

Putting the following line as the beginning of the code makes cout prints correct result:

cout.precision(7);

However, setting the precision to 6 (which is the default anyways) doesn't print the expected result.

Why this happen? I have only 1 digit after the decimal point, not 7 digits!

Upvotes: 1

Views: 56

Answers (1)

john
john

Reputation: 87957

By default, the precision is the total number of significant digits. It's not the number of digits after the decimal point. 500000.6 has seven significant digits, 500001 has only six.

Try this instead

cout << fixed << setprecision(1) << x << endl;

When used for fixed format, the precision is the number of digits after the decimal point.

Upvotes: 1

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