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Oct 27th, 2009
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converting postfix to Infix help

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I need help trying to convert a postfix expression to Infix. I have tried to search books and internet material to help me take on this task but no luck. Below is what I created, but I know it is far from right which is why I appreciate if someone can help me.


Targeted Function:


C++ Syntax (Toggle Plain Text)
  1. void toInfix(string expression)
  2. {
  3.  
  4. stackType<string> stack,here;
  5. string Infix; 
  6. string priority;
  7. string number, hold, again;
  8.  
  9. again=expression;
  10.  
  11.    ifstream inData("input.txt");
  12.    ofstream outData("output.txt");
  13.  
  14. while (getline( inData, expression ))
  15.  { 
  16.  
  17.     cout << expression;
  18.  
  19.  }
  20.  
  21. 	for (int a=0; a < expression.length(); a++) 
  22.      {
  23.  
  24. 		number = here = expression[a];
  25. 		cout << "The expression " << here << endl;
  26. 		cout << "The Infix " << Infix << endl;	
  27.  
  28.  
  29. 	       	if ( expression[a] == '+' ||  expression[a] == '-') 
  30.                 {
  31. 		 	 if (priority <= 2 ) 
  32.               {
  33.                  here.pop(); here.push();
  34.               } 
  35. 			 else 
  36.               {
  37.                  here.push();
  38.               }
  39. 	        	}
  40.  
  41.             else if ( expression[a] == '*' ||  expression[a] == '/' || expression[a] == '%' ) 
  42.               {
  43. 			if (priority == 1 ) 
  44.               {
  45.                 here=stack[0]; stack[0]=expression[a]; Infix = Infix + here; 
  46.               }  
  47. 			else 
  48.               {
  49.                 here.push;
  50.               }
  51. 		      }
  52.  
  53. 		    else if ( expression[a] == '(' ) 
  54.              {
  55.                 here.push();
  56.              }
  57.  
  58. 	    	else if ( expression[a] == ')' )
  59.             {
  60.                 here.pop();
  61.              }
  62. 		    else if ( isdigit(again[a]) ) 
  63.              {
  64. 	    	if ( isdigit(again[a+1]) ) 
  65.              {
  66. 				 int b=a+1;
  67.  while ( isdigit(again[b]) ) 
  68.     {
  69. 		hold=again[b]; 
  70. 	    number = number + hold; // number already equals the string here
  71. 		++b;
  72.     }
  73. 	    infix = infix + ' ' + number;
  74. 		 a=b-1;
  75. 			  }
  76. 			  else 
  77.                 {
  78. 				  infix = infix + ' ' + number; 
  79. 		    	}
  80.  
  81. 		} // end of else if
  82. 			cout << "\nINFIX "<<  infix << endl;
  83. 	} // end of for 
  84.  
  85. 	Infix = Infix + ' ' + stack;
  86. } 
  87.  
  88.  
  89. #endif






header file:

C++ Syntax (Toggle Plain Text)
  1. #ifndef H_StackType
  2. #define H_StackType
  3.  
  4. #include <iostream>
  5. #include <fstream>
  6. #include <cassert>
  7.  
  8. using namespace std;
  9.  
  10. template<class Type>
  11.  
  12. class stackType
  13. {
  14.  
  15.       public:
  16.              const stackType<Type>& operator=(const stackType<Type>&);
  17.              void initializeStack();
  18.              bool isEmptyStack();
  19.              bool isFullStack();
  20.              void destroyStack();
  21.              void push(const Type& newItem);
  22.              Type top();
  23.              void pop();
  24.              stackType(int stackSize = 100);
  25.              stackType(const stackType<Type>& otherStack);
  26.              ~stackType();
  27.              bool operator== (const stackType<Type>&);
  28.              bool operator!= (const stackType<Type>&);
  29.  
  30.  
  31.       private:
  32.               int maxStackSize;
  33.               int stackTop;
  34.               Type *list;
  35.               void copyStack(const stackType<Type>& otherStack);
  36.               bool isEqual(const stackType<Type>&);
  37.  
  38. };
  39.  
  40. template<class Type>
  41. void stackType<Type>::copyStack(const stackType<Type>& otherStack)
  42. {
  43.      delete [] list;
  44.      maxStackSize = otherStack.maxStackSize;
  45.      stackTop = otherStack.stackTop;
  46.  
  47.      list = new Type[maxStackSize];
  48.      assert(list != NULL);
  49.  
  50.      for(int j = 0; j < stackTop; j++)
  51.      list[j] = otherStack.list[j];
  52.  
  53. }
  54.  
  55. template<class Type>
  56. stackType<Type>::stackType(const stackType<Type>& otherStack)
  57. {
  58.       list = NULL;
  59.  
  60.       copyStack(otherStack);
  61.  
  62. }
  63.  
  64. template<class Type>
  65. const stackType<Type>& stackType<Type>::operator=(const stackType<Type>& otherStack)
  66. {
  67.       if (this != &otherStack)
  68.       copyStack(otherStack);
  69.  
  70.       return *this;
  71. }
  72.  
  73. template<class Type>
  74. void stackType<Type>::initializeStack()
  75. {
  76.      stackTop = 0;
  77. }
  78.  
  79. template<class Type>
  80. void stackType<Type>::destroyStack()
  81. {
  82.      stackTop = 0;
  83. }
  84.  
  85. template<class Type>
  86. bool stackType<Type>::isEmptyStack() 
  87. {
  88.      return(stackTop == 0);
  89. }
  90. template<class Type>
  91. bool stackType<Type>::isFullStack()
  92. {
  93.      return(stackTop == maxStackSize);
  94. }
  95.  
  96. template<class Type>
  97. void stackType<Type>::push(const Type& newItem)
  98. {
  99.      if(!isFullStack())
  100.      {
  101.          list[stackTop] = newItem;
  102.  
  103.          stackTop++;
  104.      }
  105.  
  106.      else
  107.          cerr<<"Cannot add to a full stack."<<endl;
  108. }
  109.  
  110. template<class Type>
  111. Type stackType<Type>::top()
  112. {
  113.      assert(stackTop != 0);
  114.  
  115.      return list[stackTop - 1];
  116. }
  117.  
  118. template<class Type>
  119. void stackType<Type>::pop()
  120. {
  121.      if(!isEmptyStack())
  122.      {
  123.         stackTop--;
  124.      }
  125.      else
  126.         cerr<<"Cannot remove from an empty stack."<<endl;
  127. }
  128.  
  129. template<class Type>
  130. stackType<Type>::stackType(int stackSize)
  131. {
  132.      if(stackSize <= 0)
  133.      {
  134.        cerr<<"The size of the array to hold the stack must "
  135.            <<"be positive."<<endl;
  136.        cerr<<"Creating an array of size 100."<<endl;
  137.  
  138.        maxStackSize = 100;
  139.      }
  140.  
  141.       else
  142.         maxStackSize = stackSize;
  143.  
  144.         stackTop = 0;
  145.  
  146.         list = new Type[maxStackSize];
  147. }
  148.  
  149. template<class Type>
  150. stackType<Type>::~stackType()
  151. {
  152.      delete [] list;
  153. }
  154.  
  155.  
  156.  
  157. template<class Type>
  158. bool stackType<Type>::isEqual(const stackType<Type>& otherStack) {
  159. bool bRet = false;
  160. if (otherStack.maxStackSize == maxStackSize && otherStack.stackTop == stackTop){
  161. bRet = true;
  162. for (int j = 0; j < stackTop; ++j) {
  163. if (otherStack.list[j] != list[j]) {
  164. // cout << "!=( " << j << ") " << otherStack.list[j] << "!=" << list[j];
  165. bRet = false;
  166. break;
  167. }
  168. }
  169. }
  170. return bRet;
  171. }
  172.  
  173. template<class Type>
  174. bool stackType<Type>::operator==(const stackType<Type>& otherStack) {
  175. return isEqual(otherStack);
  176. }
  177.  
  178. template<class Type>
  179. bool stackType<Type>::operator!=(const stackType<Type>& otherStack) {
  180. return !isEqual(otherStack); //!(*this == otherStack);
  181. }
  182.  
  183.  
  184.  
  185. void toInfix(string expression)
  186. {
  187.  
  188. stackType<string> stack,here;
  189. string Infix; 
  190. string priority;
  191. string number, hold, again;
  192.  
  193. again=expression;
  194.  
  195.    ifstream inData("input.txt"); // declaration of inData
  196.    ofstream outData("output.txt"); // declaration of outData
  197.  
  198. while (getline( inData, expression )) // reads words in file using getline to capture all spaces
  199. { /*something to break up line into individual character*/
  200.  
  201. cout << expression;
  202.  
  203. }
  204.  
  205. 	for (int a=0; a < expression.length(); a++) 
  206.     {
  207.  
  208. 		number = here = expression[a];
  209. 		cout << "The expression " << here << endl;
  210. 		cout << "The Infix " << Infix << endl;	
  211.  
  212.  
  213. 		if ( expression[a] == '+' ||  expression[a] == '-') 
  214.         {
  215. 			if (priority <= 2 ) 
  216.               {
  217.                  here.pop(); here.push();
  218.               } 
  219. 			else 
  220.  
  221.             here.push();
  222. 		}
  223.  
  224.         else if ( expression[a] == '*' ||  expression[a] == '/' || expression[a] == '%' ) 
  225.         {
  226. 			if (priority == 1 ) 
  227.               {
  228.                 here=stack[0]; stack[0]=expression[a]; Infix = Infix + here; 
  229.               }  
  230. 			else 
  231.  
  232.             here.push;
  233. 		}
  234. 		else if ( expression[a] == '(' ) here.push();
  235. 		else if ( expression[a] == ')' ) here.pop();
  236.  
  237. 		else if ( isdigit(again[a]) ) 
  238.         { // for dealing with multiple digits and single digit numbers
  239. 			if ( isdigit(again[a+1]) ) 
  240.              {
  241. 				 int b=a+1;
  242. 		 while ( isdigit(again[b]) ) 
  243.          {
  244. 						hold=again[b]; 
  245. 						number = number + hold; // number already equals the string here
  246. 						++b;
  247. 		 }
  248. 				 infix = infix + ' ' + number;
  249. 				 a=b-1;
  250. 			  }
  251. 			else 
  252.             {
  253. 				infix = infix + ' ' + number; 
  254. 			}
  255.  
  256. 		} // end of else if
  257. 			cout << "\nINFIX "<<  infix << endl;
  258. 	} // end of for 
  259.  
  260. 	Infix = Infix + ' ' + stack;
  261. } 
  262.  
  263.  
  264. #endif




main.cpp



#include <iostream>
#include <stdlib.h>
#include "stack.h"

using namespace std;

int main()
{

toInfix(string expression);


system("PAUSE");
return 0;
}
Last edited by NinjaLink; Oct 27th, 2009 at 1:26 am.
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