Help.. regarding string to float and float to string converion in C

[pardhu0163]

Hi guys,
I just wanted to convert the input string to float and my result get back to string format.my result is in float, long double formats).

In my stdlib.h file, atof fuynction is there, but it's occupying huge memory when i call that function and for float to string there no function at all in that lib file.

So, can any one help to implement those two converion functions..?

Thanks in advance..

[weaknessforcats]

What do you mean by "occupying huge memory"? The first requirement is that the program works. Memory usage analysis is only applied after the code works so I don't know why you are worrying about it.

To convert flot to string in C use sprintf.

[pardhu0163]

Hi sir, Thank you for your reply. I used sprintf function. It's working but not accurately.please check out my core piece of code, and if anything wrong in that, rectify me.

int main( void )
{
  char str[20];
 
  long double v=1230.0000123456f;
 
  TFT_Init();// Initialising the TFT
 
  sprintf(str, "%f", v ); 
 
  sprint(100,50,(const unsigned char*)str,GUI_WHITE,1,2);
// sprint is a function for printing a string on TFT.
}
//output:
//1230.000000
 
 

The out put what i am getting is not at all acceptable for my project. So, how to over come this?


"What do you mean by "occupying huge memory"? The first requirement is that the program works. Memory usage analysis is only applied after the code works so I don't know why you are worrying about it."

My worry is atof function is taking the little bit huge memory when i call that function. By the way i called it only once.That's why, i am thinking of replacement for atof function. I hope now you got my point.

Thank you sir.

[weaknessforcats]

This code:

long double v=1230.0000123456f;

cretes a float value 1230.000. That f on the end tells the compiler to create the constant as a float. That float is then used as the initial value of the long double.

Just omit the f:

long double v=1230.0000123456;   /*creates 1230.0000123456 */

By definition all numeric constants with a decimal part are created as double.

[pardhu0163]

Thank you sir,It's working fine.

int main( void )
{
 long double v=123456.001;
 char str[20];
 TFT_Init();                
 sprintf(str,"%Lf",v);
 sprint(100,30,str,GUI_WHITE,1,1);
 sprintf(str,"%.3f",v);
 sprint(100,50,str,GUI_WHITE,1,1);    
}
//output1 : 123456.001000
//output2 : 123456.001
 
 

Though i am getting correct result, have to remove last three zeroes in the output1(123456.001000). Here, it is taking by default 6 digits after point. But,in my case where i am passing the value to sprintf function, i don't know the exact precession.i mean, there may be fractional part(like 1.0002, 34.63876757) or may not be(1,123456).So, if i use this line of code,

sprintf(str,"%Lf",v);

i will get irrespective of actual resultant fractional part it prints a value with 6 fractional digits. That's i want to control it.

If any suggestions to do that, please let me know sir.

Thank you

regards
pardhu

[weaknessforcats]

By default the float field width is set to 6. To widen he field, to say 12, use a width specifier: %Lf12. That should allow you to see additional digits.

[pardhu0163]

yeah...that's working fine sir..

yesterday i faced rounding off problem. I need to store atleast 20 digits answer which may be in integer value or floatng value..like our pc calculator. How can i achieve this?

Thanks in advance.

Regards
Pardhu

[weaknessforcats]

Start a new thread. This is a different question from the one used to create this thread.