/** ***************************************************************************
 * @remark exploring the storage of a decimal number as a double              * 
 *                                                                            *
 *  for easy reference, this program begins with a 50-digit decimal           *
 *     0.12345678901234567890123456789012345678901234567890                   *
 *                                                                            *
 *  the true valued is stored in a double and printed                         *
 *     to various decimal places,                                             *
 *                                                                            *
 * @author Henry M. Walker                                                    *
 * @file  double-storage.c                                                    *
 * @date  Summer, 2023                                                        *
 *                                                                            *
 * @remark References                                                         *
 * @remark Consequences of Data Representation on Programming                 *
  https://blue.cs.sonoma.edu/~hwalker/courses/415-sonoma.sp25/readings/data-rep-consequences.php
 *                                                                            *
 *****************************************************************************/

#include <stdio.h>
#include <string.h>

int main ( ) {
    char * decimalString = "0.1234567890123456789012345678901234567890 ";   // digits for easy counting
  //char * decimalString = "0.2424242424242424242424242424242424242424" ;   // all digits < 5
  //char * decimalString = "0.6868686868686868686868686868686868686868" ;   // all digits > 5

    printf ("Program to explore the storage of a 40-digit decimal number\n");

    printf ("original number (stored as a sring) %s\n", decimalString);

    double decimalDouble =  0.1234567890123456789012345678901234567890 ;
  //double decimalDouble =  0.2424242424242424242424242424242424242424 ;
  //double decimalDouble =  0.6868686868686868686868686868686868686868 ;
    
    printf ("double variable 'decimalDouble' initialized to 40 decimal places\n");
    printf ("printing of double variable to successive decimal places\n");

    printf ("decimal places of double, with 15th decimal place marked (^)\n");
    printf ("places         actual decimal\n");

    char formatString [30] = {0};
    for (int i = 11; i <= 25; i++) {
        // format and double to i decimal places
        sprintf (formatString, "%%.%dlf", i);
        printf ("%3d (double)   ", i);
        printf (formatString, decimalDouble);
        printf ("\n");

        // print i+1 decimal places of actual pi string
        char decimalSubstring [30] = {0};
        strncpy(decimalSubstring, decimalString, i+2);
        printf ("    (actual)   %s\n", decimalSubstring);
        
        // highlight 15th decimal place with '^' character
        printf ("                 %15c\n\n", '^');
 
    }
  
    return 0;
}