Creating a calculator c++ [closed] - c++

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My current code is:
#include<iostream>
#include<cmath>
#include<cstdlib>
using namespace std;
int main()
{
char cAgain, type;
int x, y=0;
double addition(double num1, double num2), subtraction(double num1, double num2), division(double num1, double num2),
multiplication(double num1, double num2), exponential(double num1, double num2), num1, num2, total;
do
{
cout << "How many operations would you like to do?" << endl;
cin >> x;
if (x <= 0)
{
cout << "Error: You must have 1 or more operations." << endl;
}
else
{
while (x != 0, x--)
{
y++;
cout << "Enter in your "<<y<< " operation. (First Number (+,-,*,/,^) Second Number)" << endl;
cin >> num1 >> type >> num2;
switch (type)
{
case '+':
total = addition(num1, num2);
cout << num1 << " + " << num2 << "= " << total<< endl;
break;
case'-':
total = subtraction(num1, num2);
cout << num1 << " - " << num2 << "= " << total<< endl;
break;
case'/':
total = division(num1, num2);
cout << num1 << " / " << num2 << "= " << total<< endl;
break;
case'*':
total = multiplication(num1, num2);
cout << num1 << " * " << num2 << "= " << total << endl;
break;
case'^':
total = exponential(num1, num2);
cout << num1 << " ^ " << num2 << "= " << total << endl;
break;
}
}
}
cout << "Would you like to run the program again.(Y/N)" << endl;
cin >> cAgain;
} while (cAgain == 'Y' || cAgain == 'y');
return 0;
}
double addition(double num1, double num2)
{
double total;
total = num1 + num2;
return (total);
}
double subtraction(double num1, double num2)
{
double total;
total = num1 - num2;
return (total);
}
double division(double num1, double num2)
{
double total;
total = num1 / num2;
return (total);
}
double multiplication(double num1, double num2)
{
double total;
total = num1 * num2;
return (total);
}
double exponential(double num1, double num2)
{
double total;
total = pow(num1,num2);
return (total);
}
Currently the code works as it is suppose too.
It starts by asking
How many operations would you like to do?
You enter a number say 3
Then it ask you to enter in your operation
5+5
10
Then it ask for second
10^2
100
Then it ask for third
100-10
90
Then it ask if you want to start over and run the program again.
What I am trying to change it too is to 5+5^2-10= and it give me 20.
Essentially I want the user to be able to enter in the entire operation like 5+5^2-10= and it give me the correct answer. Allowing the user to type in a function and use '=' and return to start the calculation.

Answer 1

You can use following technique to solve an expression :
#include<iostream>
#include<cmath>
#include<stdio.h>
#include<cstdlib>
#include<map>
#include<stack>
using namespace std;
int expression_value(string str)
{
map<char,int>priority;
priority['^']=3;
priority['*']=2,priority['/']=2;
priority['+']=1,priority['-']=1;
stack<char>op_stack;
stack<int>val_stack;
int val=0;
for(int i=0;str[i];i++)
{
if(str[i]>='0'&&str[i]<='9')
val=val*10+str[i]-'0';
else
{
if(op_stack.empty()) // first operator
{
val_stack.push(val);
op_stack.push(str[i]);
}
else if(priority[op_stack.top()] < priority[str[i]]) // current operator is more prior then previous operator. so push it to stack.
{
val_stack.push(val);
op_stack.push(str[i]);
}
else // current operator is less prior then previous operator. so calculate previous operators resultant value
{
int num1,num2;
num1=val_stack.top(); val_stack.pop();
num2=val;
if(op_stack.top()=='+')
//val_stack.push(addition(num1, num2));
val_stack.push(num1 + num2);
else if(op_stack.top()=='-')
//val_stack.push(subtraction(num1, num2));
val_stack.push(num1 - num2);
else if(op_stack.top()=='*')
//val_stack.push(multiplication(num1, num2));
val_stack.push(num1 * num2);
else if(op_stack.top()=='/')
//val_stack.push(division(num1, num2));
val_stack.push(num1 / num2);
else
//val_stack.push(exponential(num1, num2));
val_stack.push(pow(num1 , num2));
op_stack.pop(); // as operator's value calculation done, pop it from the stack
op_stack.push(str[i]); // push the new operator
}
val=0;
}
}
val_stack.push(val); // last value
// calculate remaining operators value
while(!op_stack.empty())
{
int num1,num2;
num2=val_stack.top(); val_stack.pop();
num1=val_stack.top(); val_stack.pop();
if(op_stack.top()=='+')
//val_stack.push(addition(num1, num2));
val_stack.push(num1 + num2);
else if(op_stack.top()=='-')
//val_stack.push(subtraction(num1, num2));
val_stack.push(num1 - num2);
else if(op_stack.top()=='*')
//val_stack.push(multiplication(num1, num2));
val_stack.push(num1 * num2);
else if(op_stack.top()=='/')
//val_stack.push(division(num1, num2));
val_stack.push(num1 / num2);
else
//val_stack.push(exponential(num1, num2));
val_stack.push(pow(num1 , num2));
op_stack.pop();
}
return val_stack.top();
}
Here you have to pass the whole expression as string.
Operators will be stored in op_stack and value in val_stack

Answer 2

You should implement a
binary expression tree
I have just modify your program to meet your requirement:
#include <iostream>
#include <cstdio>
using namespace std;
char op;
double multiplication()
{
double product;
cin>>product;
while(1)
{
cin>>op;
if(op == '*')
{
double temp;
cin>>temp;
product *= temp;
}
else if(op == '/')
{
double temp;
cin>>temp;
product /= temp;
}
else break;
}
return product;
}
double addition()
{
double sum = multiplication();
while(op != '=')
{
if(op == '+')
sum += multiplication();
else if(op == '-')
sum -= multiplication();
else
{
cout<<"Operator error"<<endl;
return 0.0;
}
}
return sum;
}
int main()
{
char cAgain;
int x;
do
{
cout << "How many operations would you like to do?" << endl;
cin >> x;
if (x <= 0)
{
cout << "Error: You must have 1 or more operations." << endl;
}
else
{
while (x != 0, x--)
{
double result = addition();
cout<<result<<endl;
}
}
cout << "Would you like to run the program again.(Y/N)" << endl;
cin >> cAgain;
} while (cAgain == 'Y' || cAgain == 'y');
return 0;
}

Answer 3

Calculate some expressions like a+b,a-b,a^b,a*b etc is simple. But if you want to solve expressions like this:5+5^2-10,I think you need to learn something about Reverse Polish notation . It is not very difficult . Good Luck.