Question

ORIGINAL PROBLEM: A number expressed in scientific notation is represented by its mantissa (a fraction) and its exponent (an integer). Define a type sci_not_t that has separate components for these two parts. Define a function scan_sci that takes from the input source a string representing a positive number in scientific notation, and breaks it into components for storage in a sci_not_t structure. The mantissa of an input value (m) should satisfy this condition: 0.1 <= m < 1.0. Also, write functions to compute the sum, difference, product, and quotient of two sci_not_t values. All these functions should have a result type of sci_not_t and should ensure that the result’s mantissa is in the prescribed range. Define a print_sci function as well.

My question pertains to getting and properly storing the mantissa and exponent in the structure. So, the part regarding writing functions for the mathematical operations can be ignored for now. As seen in the code below, I first store the number written in scientific notation in a string as mandated by the problem. My issue is in transferring the numbers from a string to the individual parts of the structure sci_not_t. I will use 0.25000e3 as an example: user enters 0.25000e3, this is stored in a string. I use sscanf to get the double number and integer from the string and store the double part in sci.mantissa and the integer part in sci.exponent. So, 0.25000 is stored in sci.mantissa and 3 would be stored in sci.exponent. I assumed that the compiler would see these as two distinct numbers because of the 'e' between them, however the string "0.25000e3" is actually recognized by the compiler as a number in scientific notation. So, when debugging my code, I found that 250.0 is actually getting stored in sci.mantissa and nothing in sci.exponent. How can I solve this issue? (I commented out parts that can be ignored)

#include <stdio.h>
#include <math.h>
#include <string.h>
typedef struct {
   double mantissa;
   int exponent;
} sci_not_t;

sci_not_t ScanSci(char *str);
//double Sum2Sci(sci_not_t sci1, sci_not_t sci2);
int main(void)
{
   char str1[15];
   double sum;
   sci_not_t sci1, sci2;
   printf("Value 1: ");
   sci1 = ScanSci(str1);
   printf("Value 2: ");
   sci2 = ScanSci(str1);
   /*sum = Sum2Sci(sci1, sci2);
   printf("Sum: %.5e\n", sum);*/

   return 0;
}
sci_not_t ScanSci(char *str)
{
   sci_not_t sci;
   scanf("%s", str);
   sscanf(str, "%lf%d", &sci.mantissa, &sci.exponent);
   while (sci.mantissa < 0.1 || sci.mantissa >= 1.0) {
       printf("Error. Mantissa must be in range [0.1, 1)\n");
       scanf("%s", str);
       sscanf(str, "%lf%d", &sci.mantissa, &sci.exponent);
   }
   return sci;
}
//double Sum2Sci(sci_not_t sci1, sci_not_t sci2)
//{
//   return sci1.mantissa * pow(10, sci1.exponent) +
//       sci2.mantissa * pow(10, sci2.exponent);
//}

Answer 1

#include <stdio.h>
#include <math.h>
#include <string.h>
typedef struct {
double mantissa;
int exponent;
} sci_not_t;

sci_not_t ScanSci(char *str);
//double Sum2Sci(sci_not_t sci1, sci_not_t sci2);
int main(void)
{
char str1[15];
double sum;
sci_not_t sci1, sci2;
printf("Value 1: ");
sci1 = ScanSci(str1);
printf("Value 2: ");
sci2 = ScanSci(str1);
/*sum = Sum2Sci(sci1, sci2);
printf("Sum: %.5e\n", sum);*/

return 0;
}
sci_not_t ScanSci(char *str)
{
int i;
sci_not_t sci;
char mantissa[10],exponent[3]; //declaring strings mantissa and exponent
scanf("%s", str);
for(i=0;str[i]!='e';i++)
mantissa[i]=str[i]; //storing from staring character to character before e in mantissa string
i++; //changing the position from e to next character in str
int j=0;
for(i;i<strlen(str);i++)
{
exponent[j]=str[i]; //storing characters after e in exponent
j++;
}
sscanf(mantissa,"%lf",&sci.mantissa); //converting into double and storing in structure
sscanf(exponent,"%d",&sci.exponent); //converting into integer and storing in structure
printf("exponent:%d\n",sci.exponent); //printing the values
printf("mantissa:%lf\n",sci.mantissa);
while (sci.mantissa < 0.1 || sci.mantissa >= 1.0) { //condition check
printf("Error. Mantissa must be in range [0.1, 1)\nenter the value again\n");
scanf("%s", str);
for(i=0;str[i]!='e';i++)
mantissa[i]=str[i];
i++;
j=0;
for(i;i<strlen(str);i++)
{
exponent[j]=str[i];
j++;
}
sscanf(mantissa,"%lf",&sci.mantissa);
sscanf(exponent,"%d",&sci.exponent);
printf("exponent:%d\n",sci.exponent);
printf("mantissa:%lf\n",sci.mantissa);
}
return sci;
}
//double Sum2Sci(sci_not_t sci1, sci_not_t sci2)
//{
// return sci1.mantissa * pow(10, sci1.exponent) +
// sci2.mantissa * pow(10, sci2.exponent);
//}

Output: