truncating float

[EmbdedCguru]

HI , this is a question purely related to C programming. I am calculating a division between two float numbers e.g 4.00 / 3.00. Now if i answer 1.3333 , the functions returns that it is wrong. i just want to know how to truncate in Float values in C ??? here is the copy of the code: float d1,d2,d3; main( ) { srand(time(0)); // Initialize random number generator. ans = 1; while ( ans != 0 ) { /// starting of For loop //////////////// wrg =0; for ( cnt=0;cnt<3;cnt++) { d1 = float(rand()%x+2 ); d2 = float(rand()%x+2) ; printf("\n\t Solve this %f / %f :.........\n", d1, d2 ); scanf("%f", &d3); divid_cheque(d1,d2,d3); }// ending for loop printf("\n\t Do you want to continue........\n"); printf("\n\t Type 1 = continue or 0 = to terminate \n"); scanf("\n\t%d", &ans); } printf("\n Total number of wrong answers : %d out of %d \n\n", wrg, cnt); return 0; } //////////////////////Division(/) Function defined////////////////////////////////////////////////////////////////// //unsigned int division( unsigned int y, unsigned int z, unsigned int x ) // unsigned int divid_cheque( unsigned int j, unsigned int k, float l) // int divid_cheque( float j, float k, float l ) int divid_cheque( float j, float k, float l ) { float as; as=j/k; if ( l== as ) printf("\n \t Right answer..........\n"); if ( l != as ) { printf(" \n \t << WRONG ANSWER >> \n"); printf("\n \t the right answer is = %f",as); wrg++ ; // incrementing counter for wrong answers } else return (wrg); } ////////////////////////////////////////////////////////////////////////////////////////////////

[Tim Craig]

When doing comparisons with calculated float values, you generally need to decide how close is close enough. Take the absolute value of the difference between the two and see if it is less than some epsilon value which is your tolerance for "exactness".

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[Chris Losinger]

truncate at which decimal place ?

// truncate 3 places to the right of the decimal
float f1 = 4./3.;
float f2 = (float)((int)(f1 * 1000.0)) / 1000.0;

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[_Superman_]

The number of digits in a float after the decimal point cannot be truncated. You can only limit the number of digits that you want displayed. For example printf("%6.4f", 4.0/3.0); will display 1.3333.

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[beko]

Hello i use the following in order to truncate a double value (found somewhere and modified :) ) However you must be careful in here, because there could be an overflow in double fac = Num/Seed

#include <math.h>
#include <stdio.h>

double truncate(double Num, double Seed)
{
// get rational factor
double fac = Num / Seed;

// get natural factor
fac = (fac < 0) ? (ceil(fac)) : (floor(fac));
// fac = (fac < 0) ? static\_cast<int>(fac-0.5) : static\_cast<int>(fac+0.5);

// return multiple
return fac \* Seed;

}

int main()
{
double val = 4./3.;

printf("%6.4f\\n",truncate(val,1e-04));

return 0;

}