read float from string and approximation problem

[bimbam]

Hi,

I try to read a float in a string using sscanf or atof. It seems to work but then it's a bit strange when I manipulate the value obtained.

float fl;
char  str[]="1.43"

fl=atof(str);

printf("%f\n",floor(1000.0*fl) );

These lines return : 1429.000000

It seems to be due to the precision of the float type (Isn't it?).
Do you know how I can avoid that?

Regards

[JosAH]

What every computer scientist should know about floating-point arithmetic.

kind regards,

Jos

[MACKTEK]

First I want to thankyou, I had not seen the floor() function before.

Perhaps you are looking for how to format your output?

Try changing your line as follows:
printf("%.2f\n" ,(floor(1000.0* fl)) );

The %.2f tells the printf you want 2 places to the right of the decimal.

There's a whole bunch more on how to format your output here.

[Banfa]

These lines return : 1429.000000

It seems to be due to the precision of the float type (Isn't it?).
Do you know how I can avoid that?

Avoid what? you have not actually stated what you find undesirable about this output, the code is working correctly.