//=========================================================================
#define PROGRAMMER "SOLUTIONS, NoFrills"
#define PROG_CODE  "soln"
#define COURSE     "ECE-1021"
#define YEAR       (2004)
#define TERM       "Spring"
#define SECTION    (0)
#define ASSIGNMENT "HW #4A"
#define REVISION   (0)
#define TITLE      "Mystery Algorithm"
#define SUBTITLE   "Function: Square Root"
#define EMAIL      "ece1021@eas.uccs.edu"
#define FILENAME   "04a0soln.c"
//=========================================================================

// PROBLEM
//
// This is the pseudocode for a classic computational algorithm.
// It is very complete meaning that you should be able to code it
// directly from the pseudocode.

// Once it is coded, run it and try to determine what the functional
// relationship is between the input value and the output value.

// PSEUDOCODE
//
// 1) TASK: Get a number and number of sig figs from the user
// 2) TASK: Print the output header
// 3) TASK: Initialize working value
// 4) TASK: Initialize certain variables based on size of input
// 5) TASK: Generate output one digit at a time
//    5A) TASK: Determine next digit
//    5B) TASK: Update Partial Results (z and s)
//    5C) TASK: Output digit if significant and/or needed placeholder
//    5D) TASK: Output decimal point if appropriate

// RUNTIME RESULTS
//
// INPUT  SIG  OUTPUT
//  2.0    3    1.41
// 20000   3    141
// 0.002   3   0.0447
//  100    3    10.0
// 90000   3    300.
//
// The function appears to be the square root function.

//== INCLUDE FILES ========================================================
#include <stdio.h> // printf()

//== FUNCTION PROTOTYPES ==================================================
void PrintHeader(void);

//== MAIN FUNCTION ========================================================
int main(void)
{
	double x;  // value entered by user
	int sig;   // number of significant figures to print
	double y;  // working value
	double z;
	int j;
	double s;
	int k;
	double d;
	int n;

	PrintHeader();
	printf("\n"); // Print a blank line

	// 1) TASK: Get a number and number of sig figs from the user

	printf("Enter a non-negative floating point value: ");
	scanf("%lf", &x);

	printf("Enter number of significant digits to produce: ");
	scanf("%i", &sig);

	// 2) TASK: Print the output header

	printf("The output value is ");

	// 3) TASK: Initialize working value

	y = 5.0*x;

	// 4) TASK: Initialize certain variables based on size of input

	z = 1.0;
	j = 0;

	while( (y - 100.0*z)  >= 0.0 )
	{
		z = 100.0*z;
		j++;
	}

	// 5) TASK: Generate output one digit at a time

	s = 0.0;
	k = 0;

	while( k < sig )
	{
		n = 0;
		do
		{
			d = (100.0*s + 5.0*(2*n + 1))*z;
			y = y - d;
			n = n + 1;
		} while(y >= 0); // UNTIL ( y < 0 )

		y = y + d;
		n--;
		z = z / 100.0;
		s = 10*s + n;

		if( k > 0)
		{
			k++;
			printf("%i", n);
		}
		else
		{
			if( n > 0)
			{
				k++;
				printf("%i", n);
			}
			else
			{
				if( j < 0 )
					printf("%i", n);
			}
		}
		if( 0 == j )
			printf(".");
		j--;
	}

	return(0);
}

//== SUPPORT FUNCTIONS ====================================================
void PrintHeader(void)
{
	printf("========================================"
			 "=======================================\n");
	printf("Course....... %s-%i (%s %i)\n", COURSE, SECTION, TERM, YEAR);
	printf("Programmer... %s (%s)\n", PROGRAMMER, PROG_CODE);
	printf("Assignment... %s (Rev %i) (Source Code in %s)\n",
		ASSIGNMENT, REVISION, FILENAME);
	printf("Description.. %s\n", TITLE);
	printf("              %s\n", SUBTITLE);
	printf("========================================"
			 "=======================================\n");

	return;
}