hello, My program works fine but I want every time that the user add a character int the calculation section the program will print an error message and will ask the user again... I have try a lot of different things but nothing helps me... for example static_cast() and other fnc that I found and convert the stings inti double but nothing works, so If you have any ideas please let me know!! Below the code of my program....Thank you very much!!
Best Regards!!!!!!

//============================================================================
// Name        : CalculatorProject.cpp
// Author      : 
// Version     :
// Copyright   : Your copyright notice
// Description :
//============================================================================

#include <iostream>
#include <stdio.h>
#include <stdlib.h>//all the libraries that the program used some of them are not required but I used it
#include <cmath>                      // since the program output an error message
#include <unistd.h>

using namespace std;

double total = 0.0;   // variables of the whole program
double sum = 0.0;

int quit()
{
	char option2;

	cout <<"Are you sure you want to quit from the program? (Y/N): "<<endl;
    cin >> option2;    // the program ask from user if he/she wants to quit or not

	if ((option2=='Y') || (option2=='y'))   // if statement that check the  input of the user
	{ //start brackets of if statement
		cout << "GoodBye!!! C ya later!!!.. "<<endl;  // goodbye message if the user wants to quit end the program exit at next line
		return(1);
	}//end brackets of if statement
	else // else of if statement
		if ((option2=='N') || (option2=='n'))  //if statement check if the user select N/n and continues
		{ //start bracket of if statement
			cout <<"You will now return to main menu!"<<endl;  //print message that the program will return to main menu
		}// end bracket of if statement
		else  //else of the second if statement
			cout << "Error input..."<<endl; // print an error message and inform the user that the program
			cout << endl;
	return(0);
}

void addition()    //function for the addition operation...
{
	double num1,num2;
    cout << "**********"<<endl;
    cout << "*Addition*"<<endl;
	cout << "**********"<<endl;  // welcome screen
	cout << "Enter 2 numbers to calculate: "<<endl;
	cin >> num1>>num2;   // ask from the user to at 2 numbers

	
	total = num1 + num2;  // the program makes the calculation of the two numbers
	sum += total;   // save the value and keep

	cout <<"The total sum of "<<num1<<" + "<<num2<<" = "<<total<<endl;  //prints out the equation
	cout << "The total of sum is now "<<sum<<endl;

}  // end brackets of addition function....

void subtraction()   // function of subtraction...
{
	double num1,num2;    // all the variables of the fuctions

	cout <<"*************"<<endl;
	cout <<"*Subtraction*"<<endl;
	cout <<"*************"<<endl;   // welcome screen
	cout <<"Enter 2 number to calculate: "<<endl;
	cin >> num1>>num2;    //ask from user to enter 2 numbers

	total = num1 - num2;    // the program make the calculation of subtraction
    sum +=total; //save the value

    cout <<"The subtraction of "<<num1<<" - "<<num2<<" = "<<total<<endl;  //prints out the equation
    cout << "The total of sum is now "<<sum<<endl;
}

void multiplication()  // function of multiplication
{

	double num1,num2; // all the variables of the function

    cout <<"****************"<<endl;
    cout <<"*Multiplication*"<<endl;
	cout <<"****************"<<endl;    //welcome screen
	cout <<"Enter 2 number to calculate: "<<endl;
	cin >> num1>>num2;    // ask from user to enter 2 numbers

	total = num1 * num2;  // the program make the multiplication
    sum += total;    //save the value

	cout << "The total multiplication of "<<num1<<" * "<<num2<<" = "<<total<<endl;  //prints out the equation
	cout << "The total of sum is now "<<sum<<endl;

}

void division()  //  function of division
{

	double num1,num2; // all the variables of the function

	cout <<"**********"<<endl;
	cout <<"*Division*"<<endl;
	cout <<"**********"<<endl;    //welcome screen of the function
	cout <<"Enter 2 number to calculate: "<<endl;
	cin >> num1>>num2;   //ask from user to enter 2 numbers

	total = num1 / num2;  // the program make the calculation
	sum += total;  //the program save the value

	cout << "The total division of "<<num1<<" / "<<num2<<" = "<<total<<endl; //prints out the equation
	cout << "The total of sum is now "<<sum<<endl;

}

void sum_squared()   // function of the sum squared
{
	double num1,num2;             //all the variables of the function
	double displayedVal;
	displayedVal = 0.0;

	cout <<"*************"<<endl;
	cout <<"*Sum squared*"<<endl;   // welcome screen of function
	cout <<"*************"<<endl;
	cout <<"Enter 2 number to calculate: "<<endl;
	cin >> num1>>num2;  //ask from user to enter 2 numbers

	displayedVal =  pow (num1, num2);   // the program make the calculation
	sum += displayedVal;

	cout << "The total sum  squared of "<<num1<<" ^ "<<num2<<" is "<<displayedVal<<endl;  // the program prints out the equation
	cout << "The total of sum is now "<<sum<<endl;

}

void less_than_relation() // function of less then relation
{
	double num1,num2;   //all the variables of the function

	cout <<"********************"<<endl;
	cout <<"*Less than relation*"<<endl;     // welcome screen
	cout <<"********************"<<endl;
	cout <<"Enter 2 number to calculate: "<<endl;
	cin >> num1>>num2;   // ask from user to add 2 numbers

	if (num1<num2)  // if statement to check the numbers if it's less
	{   //start bracket of if statement
		total = num2;  // change the value of total into num2 if it's biggest than num1
		sum += total;

		cout <<"The "<<num1<<" is smaller (<) than "<<num2<<endl;
		cout << "The total of sum is now "<<sum<<endl;
	} // end bracket of if statement
	else   // else of if statement
		total = num1;  // change the value of total into num1
		sum+= total;

		cout << "The first number "<<num1<<" is not smaller than "<<num2<<endl;  //prints the result if the num1 is smallest than num2
		cout << "The total of sum is now "<<sum<<endl;
}

void greater_than_relation()  // function of greater than relation
{

	double num1,num2; //all variables of the function

	cout <<"***********************"<<endl;
	cout <<"*Greater than relation*"<<endl; //welcome screen of the function
	cout <<"***********************"<<endl;
	cout <<"Enter 2 number to calculate: "<<endl;
	cin >> num1>>num2;  // ask from user to enter 2 numbers

	if (num1>num2)  // if statement check if the num1 is greater of num2
	{  //start bracket of if statement
		total = num1; // change the value of total into num1 if the num1 is greater than num2
		sum +=total;

		cout <<"The "<<num1<<" is greater than (>) "<<num2<<endl;   // prints the results if the num2 is greater tha num2
		cout << "The total of sum is now "<<sum<<endl;

	} //end bracket of the if statement
	else //else of if statement
		total = num2;  // change the value of total into num2
		sum += total;

		cout << "The first number "<<num1<<" is not greater than the second number "<<num2<<endl; // prints out  the results
		cout << "The total of sum is now "<<sum<<endl;
}

void clear()
{

    char option3;

	cout <<"Are you sure you want to clear the sum?(y/n) "<<endl;;
	cin >> option3;

		if ((option3 == 'y') || (option3 == 'Y'))
	{
		total = 0.0;
		sum = 0.0;

		cout <<"Your sum now is clear!!!"<<endl;
		cout <<"The total is now "<<sum<<endl;
		}
	else

		if ((option3 == 'n') || (option3 == 'N'))
		{
		 cout <<"Your sum now is not clear. You will return into main menue!!"<<endl;
		}
		else

	    	cout <<"Error!!!You have enter an invalid input.Please enter a valid input"<<endl;

}


void calculator()   // function of the calculator

{
	char opt;  // variables of calculation function

	cout <<endl;
	cout <<"*************************************"<<endl;
	cout <<"********Welcome To Calculator********"<<endl;              //welcome screen of the void function......
	cout <<"*************************************"<<endl;              //****************************************
	cout <<"Please chose an operator you want to used: "<<endl;
	cout <<"+: Addition" <<endl;
	cout <<"-: Subtraction" <<endl;
	cout <<"*: multiplication"<<endl;
	cout <<"/: division"<<endl;                                        //All the operators options that user has available to used....
	cout <<"^: sum squared"<<endl;
	cout <<"<: less than relation"<<endl;
	cout <<">: greater than relation"<<endl;
	cout <<"c: clear sum"<< endl;
	cout <<"q: quit"<< endl;
	cin >>opt;                     //reads the opt input from the user

switch (opt)  //switch statement for the previous option that user enter
{   // start bracket of the switch statement
case '+':   // case 1 for addition
	addition();   //called the function addition...
    break;  //break of the case addition

case '-':    // case 2 for subtraction
	subtraction();  // called the subtraction function....
	break; // break of the case subtraction

case '*':   // case 3 for multiplication
	multiplication();  // called the multiplication function...
	break;  // break of the case multiplication

case '/':   // case 4 for division
	division(); // called the division function...
	break; // break of the case division

case '^':  // case 5 for sum squared...
	sum_squared();  // called the sum_squared function
	break; // break of the case sum squared

case '<':  // case 6 for the less_than_relation function
	less_than_relation();  // called the less_than_relation function
	break; // break of the case less than relation

case '>':  // case 7 for the greater_than_relation function
	greater_than_relation(); // called the greater_than_relation function
	break; // break of the case greater than relation

case 'c':  // case 8 for the clear function

	clear();
	break;  // break of the case clear

case 'q':  // case 9 for the quit
	if (quit() == 1)
		{
			exit(0);  // called the quit function
		}
	break; // break of the case quit

default:
	cout <<"Error input..Please choose an option from the above menu!!!!"<<endl;


}//end bracket of the switch case
}

int main() // int main of the program include the total retrun

{   // start bracket of int main


char option1;

while (1) // while loop for int main... every time that the program makes a calculation the program  ask again from user if wants a new operator
	{   // start bracket of while loop

cout <<"********Welcome To Calculator********"<<endl;//   welcome screen of the program......
cout <<"*************************************"<<endl;//****************************************
cout <<"Please choose one of the following: ";
cout <<endl;
cout <<"1. Calculator "<<endl;
cout <<"2. Quit "<<endl;
cin >>  option1;              //ask from user to choose one of the option that are available


	if (option1 == '1')   // if statement of the option1
	{  // start bracket of if statement
	calculator();   // called the calculator function if the option1 is 1


	} // end bracket of if statement
	else   // else of if statement

	if (option1 == '2')  // if statement of option1 check if the user choose the second option
	{ //start bracket of if statement
        if (quit() == 1)
        {
        	break; // break of the while loop to stop the while
        }

	} // end of if statement

	else // else of if statement

		// if statement... check if the input of user is not 1 or 2
		// start bracket of if statement
		cout <<"Error Input......"<<endl; // prints out an error message if the user add a wrong input

	}
	return 0;  // return to 0
} //bracket for int main

Create a function to read the numbers.
Search this site for ways to read characters in number inputs. It's been answered at least once a month for years.

WaltP I have search on website before I post my problem, it's a little bit of confiused... I have try and used

found=str.find_first_not_of("char")

but isn't works for me, also I try

boost/lecicon

library but for some reason the compiler isn't regognize the specific fun (maybe is win library I don't know) can you please be more specific?? I don't want to post the solution.. Just a hit for me because I am stuck....
Thank you anyway!!!

very simple with stringstream. for example you want to use int from string and you dont know how to convert it. use this.

string int_in_string ;
getline(cin, int_in_string);
int int_from_string;
stringstream(int_in_string) >> int_from_string ;
cout << int_from_string;
## normal int

Edited 4 Years Ago by richieking: n/a

You can try using "unsigned" but you will not be able to use negative numbers as well or you can give the numbers a range and anything outside the range will produce an error

Comments
Worthless advice

I have confused!! :P sorry guys.... Let me try to add your stringstream into one of my fncs...

void addition() //function for the addition operation...
{

int int_from_string;
string int_from_string ;
string int_in_string ;
double total;

cout << "**********"<<endl;
cout << "*Addition*"<<endl;
cout << "**********"<<endl; // welcome screen
cout <<endl;
cout << "Enter 2 numbers to calculate: "<<endl;
getline(cin, int_in_string); // ask from the user to at 2 numbers
getline(cin, int_form_string);

stringstream(int_in_string) >> int_from_string ;
if ((stringstream!=int_from_string) || (stromgstream!=int_in_string))
{
cout <<"Error input.. Please select only numbers.."<<endl;
}
else

total = int_in_string + int_in_string; // the program makes the calculation of the
sum += total; // save the value and keep
 
cout <<"The total sum of "<<int_in_string<<" + "<<int_form_string<<" = "<<total<<endl; //prints out the 
cout << "The total of sum is now "<<sum<<endl;
} // end brackets of addition function....
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