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#define Sentinel ‘=’
#define SIZE 15
enum ItemIDTYPE {INVALIDCHAR, LT_PAREN, RT_PAREN, OPERAND, OPERATOR, SENTINEL};
struct EXPRESSION
{
char items[SIZE];
int index;
};
#include "D_Stack.h"
#include <iostream>
#include<fstream>
#include<string>
using namespace std;
void Read(EXPRESSION&);
void Convert(const EXPRESSION&,EXPRESSION&);
float Evaluate(const EXPRESSION&);
void print(const EXPRESSION&,const EXPRESSION&,float);
bool item_HEAVIER_top (char,int);
ItemIDTYPE FindItemID(char);
void ProcessOperator(char);
float PopComputePush(char);
void PopUptoLtParen(char);
void EmptyStack(char);
int main()
{
EXPRESSION Infix, Postfix;
float Value;
ifstream infile;
infile.open("E:\\expressions.txt");
while(!infile)
{
Read(Infix);
Convert(Infix,Postfix);
Value =Evaluate(Postfix);
print(Infix, Postfix, Value);
}
infile.close();
system("pause");
return 0;
}
void Convert(EXPRESSION const& Infix,EXPRESSION& Postfix)
{
char item;
ItemIDTYPE itemID;
Stack<char>OpStack;
while(itemID!=SENTINEL)
{
item=Infix.items[Infix.index];
itemID= FindItemID(item);
switch (itemID)
{
case OPERAND:cout<<OPERAND; break;
case LT_PAREN:OpStack.Push('('); break;
case RT_PAREN:PopUptoLtParen(item); break;
case OPERATOR:ProcessOperator(item); break;
case INVALIDCHAR: cout<<"Invalid char"<<endl;break;
}
}
EmptyStack(item);
}
void ProcessOperator(char item)
{
int Top=0;
Stack<char>OpStack;
while (OpStack.IsFull())
{
OpStack.Pop(item);
if (item_HEAVIER_top(item, Top))
{
OpStack.Push(item);
break;
}
else
cout<<OpStack<<endl;
OpStack.Push(item);
}
}
float Evaluate(EXPRESSION const& Postfix)
{
float value;
char item;
Stack<float>opndStack;
ItemIDTYPE itemID;
while(Postfix.items[Postfix.index]!=0)
{
item=Postfix.items[Postfix.index];
itemID = FindItemID(item);
switch (itemID)
{
case OPERAND:opndStack.Push(item); break;
case OPERATOR:PopComputePush(item); break;
}
}
opndStack.Pop(value);
}
ItemIDTYPE FindItemID(char item)
{
ItemIDTYPE itemID;
if(item='+')
itemID=OPERATOR;
else if(item='-')
itemID=OPERATOR;
else if(item='*')
itemID=OPERATOR;
else if(item='/')
itemID=OPERATOR;
else if(item='(')
itemID=LT_PAREN;
else if(item=')')
itemID=RT_PAREN;
else
itemID=OPERAND;
}
void PopUptoLtParen(char item)
{
ItemIDTYPE itemID;
Stack<char>OpStack;
while(itemID!=LT_PAREN)
{
OpStack.Pop(item);
}
cout<<OpStack<<endl;
}
bool item_HEAVIER_top (char item,int top)
{
int level0 = 0;
int level1 = 1;
int level2 = 2;
if (item == '*')
return level2;
else if (item == '/')
return level2;
else if (item== '+')
return level1;
else if (item == '-')
return level1;
else
return level0;
}
float PopComputePush(char item)
{
float a;
float b;
char c;
Stack<char>OpStack;
Stack<float>opndStack;
opndStack.Pop(a);
opndStack.Pop(b);
OpStack.Pop(c);
float total=(a,c,b);
opndStack.Push(total);
}
void Read(EXPRESSION& Infix)
{
ifstream infile;
infile>>Infix.items[Infix.index];
cout<<Infix.items[Infix.index];
}
void print(EXPRESSION const& Infix,EXPRESSION const& Postfix,float Value)
{
cout<<"the infix is"<<Infix.items[Infix.index]<<endl;
cout<<"the postfix is"<<Postfix.items[Postfix.index]<<endl;
cout<<"The value is "<<Value;
}
void EmptyStack(char item)
{
ItemIDTYPE itemID;
Stack<char>OpStack;
while(itemID!=SENTINEL)
{
OpStack.Pop(item);
}
cout<<OpStack<<endl;
}
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