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  1. //*****************************************************************************
  2. // Postfix expression evaluation
  3. // 11/13/2012
  4. // by DJH
  5. //
  6. // all applicable copyrights apply
  7. //
  8. // this program evaluates an input postfix string
  9. // 
  10. //
  11. // created using Dev-C++ 5.2.0.3
  12. //*****************************************************************************
  13.  
  14. // ----------------------------------libraries---------------------------------
  15.  
  16. #include <iostream>    			// For cin, cout and endl
  17. #include <string>
  18. #include <cctype>
  19. #include <vector>
  20. #include <sstream>
  21. #include <cstdlib>
  22. #include <cmath>
  23. #include <iomanip>
  24.  
  25. using namespace std;
  26. // ------------------------------ Globals -------------------------------------
  27. string postfix;
  28.  
  29. // --------------------------- stack class ------------------------------------
  30. class Stack{
  31. public:
  32.   enum {MaxStack = 50};
  33.   void init() {top = -1;}
  34.   void push( double p ){
  35.     if ( isFull() ) {
  36.       cerr << "Full Stack. DON'T PUSH\n";
  37.       return;
  38.     }
  39.     else {
  40.       arr[ ++top ] = p;
  41.       cout << "Just pushed " << p << endl;
  42.       return;}
  43.   }
  44.   int pop() {
  45.     if (isEmpty() ) {
  46.       cerr << "\tEmpty Stack. Don't Pop\n\n";
  47.       return 1;
  48.     }
  49.     else 
  50.       return arr[top--];
  51.   }
  52.   bool isEmpty() {return top < 0 ? 1 : 0;}
  53.   bool isFull() {return top >= MaxStack -1 ? top : 0;}
  54.   void dump_stack() {
  55.     cout << "The Stack contents, from top to bottom, from a stack dump are: " << endl;
  56.     for (int s = top; s >= 0; s--)
  57.       cout << "\t\t" << arr[s] << endl;
  58.   }
  59. private:  
  60.   int top;
  61.   double arr[MaxStack];
  62. }pStack;
  63. // ------------------------------ end stack class -----------------------------
  64.  
  65. // -----------------------------function prototypes----------------------------
  66. void evalPostfix (string);
  67. double decimalEvaluate (string, int, double);
  68. // ----------------------------------------------------------------------------
  69.  
  70. // -----------------------------------Main()-----------------------------------
  71. int main()
  72. {
  73. 	cout << "Enter a postfix expression\n\t (without spaces - using '_' for delimiters):\n\t";
  74. 	cout << "For example: 8_5_3_+_*_2_/_5_+\n" << endl;
  75. 	getline(cin, postfix);
  76.  
  77. //	postfix = "7_2_*_5_+_2_*";
  78. 	cout << "You entered: " << postfix << endl;
  79.  
  80. int c=0;
  81.  
  82. while ( postfix[c] !='\0' )
  83. 	{
  84. 	++c;			// this loop counts the characters in the input string including whitespace
  85. 	}
  86.  
  87. cout <<	"\tThe string length is:\t" << c << endl;
  88. evalPostfix (postfix);
  89. int result = pStack.pop();
  90. cout << "The result of the postfix expression is: " << result << endl;
  91.  
  92.  
  93. /*
  94. stack commands:
  95. 	Stack a_stack; 			// creates new stack
  96. 	a_stack.init();			// initializes top element
  97. 	a_stack.pop(); 			// pops top of stack
  98. 	a_stack.push(n); 		// push element to top of stack
  99. 	a_stack.dump_stack(); 	// displays the contents of the stack from top to bottom
  100. */	
  101. 	return 0;
  102. 	cin.get();
  103. }
  104.  
  105.  
  106.  
  107. // --------------------------------end of Main()-------------------------------
  108.  
  109.  
  110. // ------------------------------functions follow------------------------------
  111. void evalPostfix (string)
  112. {
  113. 	double ch=0,dc=0,b=0,a=0,d=0;
  114. 	double tempDC=0;
  115. 	double tempDCD=0;
  116. 	char op;
  117. 	int i=0,j=0,k=0,m=0,n=0,q=0;
  118. 	while (postfix[i] != '\0')
  119. 	{
  120.  
  121. 	if (postfix[i] == '_') {i++;}
  122.  
  123. 	else if (isdigit (postfix[i]))
  124. 			{
  125. 				ch = postfix[i] - '0'; // for numbers only
  126. 				j=i+1;
  127. 				while (postfix[j] != '_')
  128. 				{
  129. 					if (isdigit (postfix[j]))
  130. 					{
  131. 					ch = ch*10 + (postfix[j] - '0');
  132. 					k=j+1;
  133. 					 if (postfix[k] == '.') // this accounts for decimals by skipping the '.' and conducting operations on trailing numbers
  134. 						{
  135. 						dc=0;
  136. 						decimalEvaluate (postfix, k, dc);
  137. 						dc = tempDC / tempDCD;
  138. 						d=ch+dc;
  139. 						k++;
  140.  
  141. 						}
  142. 					j=k-1;
  143. 					j++;					
  144. 					}
  145. 				}
  146. cout << "Post decimal function k: " << k << endl;
  147. cout << "Post decimal function dc: " << setprecision (12) << dc << endl;
  148. cout << "Post decimal function d: " << d << endl;
  149. 				pStack.push(d);
  150. 				i=j-1;
  151. 				i++;
  152. 			}
  153. 	else if (postfix[i] == '+' || postfix[i] == '-' || postfix[i] == '*' || postfix[i] == '/' || postfix[i] == '^')
  154. 			{  
  155. 			b=pStack.pop();
  156. 			a=pStack.pop();
  157. 			op = postfix[i]; // for operators only
  158. 			switch(op)
  159. 				{
  160. 				case '+':pStack.push(a+b);
  161. 					break;
  162. 				case '-':pStack.push(a-b);
  163. 					break;
  164. 				case '*':pStack.push(a*b);
  165. 					break;
  166. 				case '^':pStack.push(pow(a,b));
  167. 					break;
  168. 				case '/':if(b==0)
  169. 					 {
  170. 						 cout << "Division by zero not allowed!" << endl;
  171. 						 cin.get();
  172. 						 exit(0);
  173. 					 }
  174. 					 pStack.push(a/b);
  175. 				default:cout << "Invalid Operation" << endl;
  176. 				}
  177. 			i++;
  178. 			}
  179.  
  180. 	}
  181. }
  182. // ----------------------------------------------------------------------------
  183.  
  184. double decimalEvaluate (string postfix, int k, double dc)
  185. {
  186. 	dc=0;
  187. 	double tempDC=0;
  188. 	double tempDCD=0;
  189.  
  190. 	int n=0, m=0,lenDC=0;
  191.  
  192. 	n=k;
  193.  
  194. while ( postfix[n] != '_' )
  195. 	{
  196. 	if ((isdigit (postfix[n]))== false)
  197. 		{
  198. 		n++;
  199. 		}
  200. cout << "This step (1) n: " << n << endl;		
  201. 	if (isdigit (postfix[n]))
  202. 		{
  203. 		m=n;
  204. 		while ( postfix[m] != '_' ) // assumes characters between a '.' and '_' are all digits (may need to check)
  205. 			{
  206. 			lenDC++;
  207. 			m++;			// this loop counts the digits in the input trailing a decimal point
  208. 			}
  209. cout << "This step (2) m: " << m << endl;
  210. cout << "This step (2) lenDC: " << lenDC << endl;								
  211. 		while ((postfix[n]) != '_')
  212. 			{
  213. 			tempDC = tempDC*10 + (postfix[n]) - '0';
  214. 			n++;
  215. 			}
  216. cout << "This step (3) n: " << n << endl;
  217. cout << "This step (3) tempDC: " << tempDC << endl;
  218. 		}
  219. 	k=n;
  220.  
  221. 	tempDCD = pow(10,lenDC);
  222.  
  223. 	dc = tempDC / tempDCD;
  224.  
  225. cout << "This step (4) k: " << k << endl;
  226. cout << "This step (4) tempDCD: " << tempDCD << endl;
  227. cout << "This step (4) tempDC: " << tempDC << endl;
  228. cout << "This step (4) dc: " << dc << endl;
  229. 	}
  230. 	return dc,k,tempDC,tempDCD;
  231. }
  232.  
  233.  
Success #stdin #stdout 0.02s 2868KB
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17.3_13.7_+
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Enter a postfix expression
	 (without spaces - using '_' for delimiters):
	For example: 8_5_3_+_*_2_/_5_+

You entered: 17.3_13.7_+
	The string length is:	11
This step (1) n: 3
This step (2) m: 4
This step (2) lenDC: 1
This step (3) n: 4
This step (3) tempDC: 3
This step (4) k: 4
This step (4) tempDCD: 10
This step (4) tempDC: 3
This step (4) dc: 0.3
Post decimal function k: 4
Post decimal function dc: nan
Post decimal function d: nan
Just pushed nan
This step (1) n: 8
This step (2) m: 9
This step (2) lenDC: 1
This step (3) n: 9
This step (3) tempDC: 7
This step (4) k: 9
This step (4) tempDCD: 10
This step (4) tempDC: 7
This step (4) dc: 0.7
Post decimal function k: 9
Post decimal function dc: nan
Post decimal function d: nan
Just pushed nan
Just pushed -4294967296
The result of the postfix expression is: -2147483648
https://ideone.com/z330hh
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
secret

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