How I can fix ISO C++ does not allow conversion from string literal to char*?

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int Priority(char x){
    if (x=='+' || x=='-')
        return 1;
    else if (x=='*'||x=='/')
        return 2;
    else if (x=='^')
        return 3;
    else
        return -1;
}
int InfixToPostfix(char expression[]){
    char *e,x;
    Stack<char> stack(10);
    e=expression;
    while(*e!='\0'){
        if ((*e >= 'a' && *e <= 'z') || (*e >= 'A' && *e <= 'Z')
            || (*e >= '0' && *e <= '9'))
            cout<<*e;
        else if (*e=='(')
            stack.Push(*e);
        else if (*e==')'){
            while ((x=stack.Pop())!='(')
                cout<<"x";
        }
        else{
            while(Priority(stack.Top())>= Priority(*e))
                cout<<stack.Pop();
            stack.Push(*e);
        }
 e++;
    }
   
    while (!stack.IsEmpty()){
        cout<<stack.Pop();
    }
}
int main(){
    InfixToPostfix("(a+(b*(d+2)))");
}

What I have tried:

int Priority(char x){
    if (x=='+' || x=='-')
        return 1;
    else if (x=='*'||x=='/')
        return 2;
    else if (x=='^')
        return 3;
    else
        return -1;
}
int InfixToPostfix(char expression[]){
    char *e,x;
    Stack<char> stack(10);
    e=expression;
    while(*e!='\0'){
        if ((*e >= 'a' && *e <= 'z') || (*e >= 'A' && *e <= 'Z')
            || (*e >= '0' && *e <= '9'))
            cout<<*e;
        else if (*e=='(')
            stack.Push(*e);
        else if (*e==')'){
            while ((x=stack.Pop())!='(')
                cout<<"x";
        }
        else{
            while(Priority(stack.Top())>= Priority(*e))
                cout<<stack.Pop();
            stack.Push(*e);
        }
  e++;
    }
  
    while (!stack.IsEmpty()){
        cout<<stack.Pop();
    }
}
int main(){
    InfixToPostfix("(a+(b*(d+2)))");
}

Posted 26-Apr-22 8:26am

Rishabh Vishwakarma 2022

Updated 26-Apr-22 9:40am

v2

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Comments

Richard MacCutchan 26-Apr-22 15:14pm

Which line causes the error?

Rishabh Vishwakarma 2022 26-Apr-22 15:21pm

InfixToPostfix("(a+(b*(d+2)))");

Richard MacCutchan 26-Apr-22 15:27pm

That does not make sense. Which compiler are you using?

Rishabh Vishwakarma 2022 26-Apr-22 15:38pm

I am using Clion ide and my output is abd2xxx

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Rick York · Answer 1 · 2022-04-26T09:40:00

Solution 1

The problem a string literal value is constant and the function is not set up for that. Here is how you can fix it :

C++

int InfixToPostfix( const char expression[] ){
    const char *e;
    Stack<char> stack(10);
    e=expression;
    while(*e!='\0'){
        if ((*e >= 'a' && *e <= 'z') || (*e >= 'A' && *e <= 'Z')
            || (*e >= '0' && *e <= '9'))
            cout<<*e;
        else if (*e=='(')
            stack.Push(*e);
        else if (*e==')'){
            while ((x=stack.Pop())!='(')
                cout<<"x";
        }
        else{
            while(Priority(stack.Top())>= Priority(*e))
                cout<<stack.Pop();
            stack.Push(*e);
        }
    }
    e++;
    while (!stack.IsEmpty()){
        cout<<stack.Pop();
    }
}

It basically amounts to making the function take a const char pointer.

Posted 26-Apr-22 9:40am

Rick York

Comments

Rishabh Vishwakarma 2022 26-Apr-22 15:52pm

#include <iostream>
#include <algorithm>
using namespace std;

template <class t="">
class Stack{
private:
int top;
int capacity;
T* stack;
public:
Stack(int capacity);
bool IsEmpty()const;
int Size()const;
void Push(const T& data);
T& Pop();
T& Top()const;
};

template <class t="">
Stack<t>::Stack(int stackCapacity):capacity(stackCapacity) {
if (stackCapacity<1)throw "Stack Capacity must be >0";
stack=new T[capacity];
top=-1;
}

template <class t="">
inline bool Stack<t>::IsEmpty() const { return top==-1;}

template <class t="">
inline int Stack<t>::Size() const { return top+1;}

template <class t="">
inline T& Stack<t>::Top() const {
if (IsEmpty())throw "Stack is Empty";
return stack[top];
}
template<class t="">
void ChangeSize(T*&a,const int oldSize,const int newSize){
if (newSize<0)throw "NewLength must be >=0";
T* temp=new T[newSize];
int number= min(oldSize,newSize);
copy(a,a+number,temp);
delete []a;
a=temp;
}

template <class t="">
void Stack<t>::Push(const T &data) {
if (top==capacity-1){
ChangeSize(stack,capacity,2*capacity);
capacity=2*capacity;
}
stack[++top]=data;
}

template <class t="">
T& Stack<t>::Pop(){
if (IsEmpty())throw "Stack is Empty";
return stack[top--];
}

int Priority(char x){
if (x=='+' || x=='-')
return 1;
else if (x=='*'||x=='/')
return 2;
else if (x=='^')
return 3;
else
return -1;
}
int InfixToPostfix( const char expression[] ){
const char *e;
char x;
Stack<char> stack(10);
e=expression;
while(*e!='\0'){
if ((*e >= 'a' && *e <= 'z') || (*e >= 'A' && *e <= 'Z')
|| (*e >= '0' && *e <= '9'))
cout<<*e;
else if (*e=='(')
stack.Push(*e);
else if (*e==')'){
while ((x=stack.Pop())!='(')
cout<<"x";
}
else{
while(Priority(stack.Top())>= Priority(*e))
cout<

CPallini 27-Apr-22 2:01am

5.