When I assign int to float variable, then I print the variable. Why the output is 1 but not 1.0?-CodePudding

#include <iostream>
int main()
{
    float i = 1;
    std::cout << i;
    return 0;
}

I read C Primer, it said when we assign int to float variable, the fractional part is recorded as 0. Then I try the code above, I couldn't understand the output.

CodePudding user response：

Well, it's up to std::cout to print that 0 or not, not i itself. std::cout choose to not print that 0, so all you can see is 1.

You can change it using <iomanip>'s std::setprecision():

#include <iostream>
#include <iomanip>

int main()
{
    float i = 1;
    std::cout << std::fixed << std::setprecision(1) << i;
    return 0;
}

This above prints:

1.0

CodePudding user response：

Why the output is 1 but not 1.0?

Because you didn't specify such formatting, and because that's not how floats are formatted by default. You can change the formatting using io manipulators.

CodePudding user response：

You could try to use printf to write a formatted number to stdout.

#include <iostream>

int main()
{
    float i = 1;
    printf("%lf", i);
    
    return 0;
}

output:

1.000000