// asst5v1.cpp       ALGORITHM DESIGN 306
// arrays of infix strings, postfix strings, operands and operand-values
#include <iostream>
#include <iomanip>             //for setw function to format output
#include<stdio.h>				//needed for printf
#include<cstring>
using namespace std;		   //standard namespace

int idx;
const int LMAX = 50;        //maximum number of infix strings in array
const int NMAX = 30;        //maximum size of each infix string
const int LSIZE = 5;        //actual number of infix strings in the array infix
const int NUMOPNDS = 10;    //number of different operands i.e. A through J
const int MAXSTACK = 100;   //maximum number of items allowed in the stack structures
//array of infix strings
char ifx[NMAX];
char pfx[NMAX];
char infix[LMAX][NMAX] = { "A+B-C",
"(A+B)*(C-D)",
"A$B*C-D+E/F/(G+H)",
"((A+B)*C-(D-E))$(F+G)",
"A-B/(C*D$E)" };
//array of postfix strings
char postfix[LMAX][NMAX] = { "AB+C-",
"AB+CD-*",
"AB$C*D-EF/GH+/+",
"AB+C*DE--FG+$",
"ABCDE$*/-" };

//arrays for the operands and their values
char opnd[NUMOPNDS] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J' };
int opndval[NUMOPNDS] = { 3, 1, 2, 5, 2, 4, -1, 3, 7, 187 };
int j;

struct OPERAND_STACK
{
	int top;
	double items[MAXSTACK];
};
OPERAND_STACK opndstk;

void opndpush(double);
double opndpop();
bool opnEmpty();
void convert(char[], char[]);
double evaluation(char[],int[NUMOPNDS],double val);

int main()
{
	double val;
	opndstk.top = -1;
	/*************************************************************************
	PRINT OUT THE INFIX EXPRESSIONS
	**************************************************************************/
	printf("%40s\n\n", "OPERANDS AND THEIR VALUES:");
	for (j = 0; j<NUMOPNDS; j++)
		printf("%5c", opnd[j]);
	printf("\n\n");
	for (j = 0; j<NUMOPNDS; j++)
		printf("%5i", opndval[opnd[j] - 'A']); //is not SIMPLER to just use j ONLY as the subscript?
	//Q:  why the more complex syntax?   A:  j ONLY assumes that operands are in lexical order
	printf("\n\n\n");
	printf("RESULTS:\n\n");

	printf("%25s%25s%15s\n", "INFIX EXPRESSION", "POSTFIX RESULT", "Value");
	printf("%25s%25s%15s\n", "-----------------", "---------------", "-----");
	for (idx = 0; idx < LSIZE; idx++)  //display name strings & corresponding weights
	{
		strcpy(ifx, infix[idx]);
		convert(ifx, pfx);
		val = evaluation(postfix[NMAX], opndval, val);
		printf("%25s%25s%15g\n", ifx, pfx, val);
	}
	/*************************************************************************
	PRINT OUT THE OPERANDS AND THEIR VALUES
	**************************************************************************/
	system("PAUSE");
	return 0;
}
/****************************************************************************
CONVERSION FUNCTION: INFIX TO POSTFIX NOTATION
****************************************************************************/
void convert(char ifx[], char pfx[])
{
	strcpy(pfx, postfix[idx]);
}
/****************************************************************************
FUNCTION TO DISPLAY INFIX AND POSTFIX EXPRESSIONS
****************************************************************************/
/****************************************************************************
FUNCTION TO EVALUATE THE POSTFIX EXPRESSION
****************************************************************************/
double evaluation(char postfix[NMAX], int opndval[NUMOPNDS], double val)
{
	char s;
	double op1;
	double op2;
	int k = 0;

	while(postfix[k] != '/0')
	{
		s = postfix[k];
		if(isalpha(s))
			opndpush(opndval[s - 'A']);
		else
		{
			op2 = opndpop();
			op1 = opndpop();
			switch(s)
			{
			case '+': val = op1 + op2;
					break;
			case '-': val = op1 - op2;
				break;
			case '/': val = op1 / op2;
				break;
			case '*': val = op1 * op2;
				break;
			case '$': val = pow(op1,op2);
				break;
			default: break;
		    }
			opndpush(val);
		}
			k++;
	}
	return val = opndpop();
}

void opndpush(double c)
{
	opndstk.top++;
	opndstk.items[opndstk.top] = c;
}

double opndpop()
{
	double c;
	c = opndstk.items[opndstk.top];
	opndstk.top--;
	return c;
}

bool opnEmpty()
{
	bool r;
	if (opndstk.top == -1)
		r = true;
	else
		r = false;
	return r;
}