'string' to 'int' and 'int' to 'string'? Please Help!?

Question

lxXTaCoXxl 26 Posting Whiz in Training

11 Years Ago

I'm trying to convert a number to a string then back to a number to perform math, then back to a string to return it to the user. I don't understand the problem because this is how my friend did it (that I can remember and it worked for him). Basically if someone can help me with this topic it would be apreciated!

std::string Resistor::CalculateResistance(int Digit1, int Digit2, int Multiplier, int Tolerance) {
    std::istringstream buffer;
    buffer >> Digit1;

    std::string x = buffer.str; // Problem
    buffer >> Digit2;
    x += buffer.str; // Problem

    double y = atof(x.c_str) * Multiplier; // Problem

    std::istringstream buffer2;
    std::string z = "";

    if (y > 999 && y < 999999) {
        y /= 1000;
        buffer2 >> y;
        z = buffer2.str + "KΩ" + Tolerances[Tolerance]; // Problem
        return z;
    }

    else if (y > 999999 && y < 999999999) {
        y /= 1000000;
        buffer2 >> y;
        z = buffer2.str + "MΩ" + Tolerances[Tolerance]; // Problem
        return z;
    }

    return "An error occured, please try again...\n";
}

The errors being thrown are:

error C3867: 'std::basic_istringstream<_Elem,_Traits,_Alloc>::str': function call missing argument list; use '&std::basic_istringstream<_Elem,_Traits,_Alloc>::str' to create a pointer to member

error C2679: binary '+=' : no operator found which takes a right-hand operand of type 'overloaded-function' (or there is no acceptable conversion)

Thanks,
Jamie

c++

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Latest Post 11 Years Ago Latest Post by NathanOliver

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Lucaci Andrew 140 Za s|n

11 Years Ago

Have you checked this code snippet? http://www.daniweb.com/software-development/cpp/code/425707/simple-string-to-int-and-int-to-string-conversion

deceptikon 1,790 Code Sniper

11 Years Ago

x += buffer.str; // Problem

str() is a member function: x += buffer.str();

double y = atof(x.c_str) * Multiplier; // Problem

c_str() is also a member function: 'double y = atof(x.c_str()) * Multiplier;'

Repeat that fix for every usage.

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lxXTaCoXxl 26 Posting Whiz in Training · Answer 1 · 2012-07-02T19:28:28+00:00

Okay so after looking at that link I threw together a class that follows the same principles. However it's giving me an error saying unresolved external symbol in Main.obj. I'll post the entire source and hopefully we can get this fixed. I appreciate all the help!

Error: error LNK2019: unresolved external symbol "public: int __thiscall Convert::ToInt32(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> >)" (?ToInt32@Convert@@QAEHV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z) referenced in function "public: class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > __thiscall Resistor::CalculateResistance(int,int,int,int)" (?CalculateResistance@Resistor@@QAE?AV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@HHHH@Z)

Location: Main.obj

Error: error LNK1120: 2 unresolved externals
Location: ResistorCalc.exe

// Main.cpp
#include <iostream>
#include "Resistor.h"

using namespace std;

int main() {
    Resistor r1;
    int b1;
    int b2;
    int b3;
    int b4;

    cout << "Please input the color of the first three bands using the following numbers:\n";
    cout << "Black - 0\n";
    cout << "Brown - 1\n";
    cout << "Red - 2\n";
    cout << "Orange - 3\n";
    cout << "Yellow - 4\n";
    cout << "Green - 5\n";
    cout << "Blue - 6\n";
    cout << "Violet - 7\n";
    cout << "Gray - 8\n";
    cout << "White - 9\n";

    cin >> b1 >> b2 >> b3;

    cout << "Please input the color of the tolerance band color using the following numbers:\n";
    cout << "Gold - 0\n";
    cout << "Silver - 1\n";
    cout << "None - 2\n";

    cin >> b4;

    cout << "Your resistor is: " << r1.CalculateResistance(b1, b2, b3, b4);

    system("pause");
}

// Resistor.h
#include <string>
#include "Convert.h"

class Resistor {
    public:
        Resistor();
        int Bands[10];
        int Multipliers[10];
        int Tolerances[3];

        std::string CalculateResistance(int, int, int, int);
};

Resistor::Resistor() {
        // Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Gray, White
        for (int i = 0; i < 10; i++)
            Bands[i] = i;

        for (int x = 0; x < 10; x++) {
            for (int y = 0.01; y < 10000000; y *= 10)
                Multipliers[x] = y;
        }

        // Gold, Silver, None
        for (int x = 0; x < 3; x++) {
            for (int y = 5; y < 20; y *= 2)
                Tolerances[x] = y;
        }
}

std::string Resistor::CalculateResistance(int Digit1, int Digit2, int Multiplier, int Tolerance) {
    Convert convert;
    std::string Additive = convert.ToString(Digit1) + convert.ToString(Digit2);

    double y = convert.ToInt32(Additive) * Multiplier;

    std::string z = "";

    if (y >= 0 && y < 999) {
        z = convert.ToString(y) + "Ohm +- " + convert.ToString(Tolerances[Tolerance]);
        return z;
    }

    else if (y > 999 && y < 999999) {
        y /= 1000;

        z = convert.ToString(y) + "K Ohm +- " + convert.ToString(Tolerances[Tolerance]);
        return z;
    }

    else if (y > 999999 && y < 999999999) {
        y /= 1000000;

        z = convert.ToString(y) + "M Ohm +- " + convert.ToString(Tolerances[Tolerance]);
        return z;
    }

    return "error 0: result was out of range.\n";
}

// Convert.h
#include <sstream>
#include <string>

using namespace std;

class Convert {
public:
    bool IsInt32(string);
    int ToInt32(string);
    string ToString(int);
};

    bool IsInt32(string s) {
        string hyphen = "-";

        if (s[0] == hyphen[0])
            s.erase(0, 1);

        for (int i = 0; i < (int)s.size(); i++)
            if (isdigit(s[i] == 0)) return false;

        return true;
    }

    string ToString(int i) {
        stringstream s;
        s << i;

        return s.str();
    }

    string ToString(double d) {
        stringstream s;
        s << d;

        return s.str();
    }

    int ToInt32(string s) {
        stringstream i;
        int returnVal;

        if (IsInt32(s)) {
            i << s;
            i >> returnVal;
            return returnVal;
        }

        else return -1;
    }

Thanks,
Jamie

deceptikon 1,790 Code Sniper Team Colleague Featured Poster · Answer 2 · 2012-07-02T19:33:10+00:00

Look in Convert.h and ask yourself how to define a member function outside of the class definition. That's your error. You'll also have overloading issues because the return type doesn't make a function signature unique.

DeanMSands3 69 Junior Poster · Answer 3 · 2012-07-02T19:48:41+00:00

Here's a hint:
Line 114:bool IsInt32(string s) {
Should look like: bool Convert::IsInt32(string s) {

This is not the only change you will have to make.

Later on, I suggest you change the methods in your Convert class into static's so you can call them directly from the class instead of creating a Convert object everytime. But save that for later. For now, this will probably only be confusing. Right now, just get it working. Then, get it working nicely.

lxXTaCoXxl 26 Posting Whiz in Training · Answer 4 · 2012-07-02T20:00:27+00:00

Okay so I got the application to successfully compile, however there is still a problem; the application is not printing anything I told it to in the main() function. It just sits there and I'm thinking it might be infinite loop or recursion because I can't even type anything into the terminal?

// Main.cpp
#include <iostream>
#include <string>
#include "Resistor.h"

using namespace std;

int main() {
    Resistor r1;
    int b1;
    int b2;
    int b3;
    int b4;

    cout << "Please input the color of the first three bands using the following numbers:\n";
    cout << "Black - 0\n";
    cout << "Brown - 1\n";
    cout << "Red - 2\n";
    cout << "Orange - 3\n";
    cout << "Yellow - 4\n";
    cout << "Green - 5\n";
    cout << "Blue - 6\n";
    cout << "Violet - 7\n";
    cout << "Gray - 8\n";
    cout << "White - 9\n";

    cin >> b1 >> b2 >> b3;

    cout << "Please input the color of the tolerance band color using the following numbers:\n";
    cout << "Gold - 0\n";
    cout << "Silver - 1\n";
    cout << "None - 2\n";

    cin >> b4;

    cout << "Your resistor is: " << r1.CalculateResistance(b1, b2, b3, b4);

    system("pause");
}

// Resistor.h
#include <string>
#include "Convert.h"

class Resistor {
    public:
        Resistor();
        int Bands[10];
        int Multipliers[10];
        int Tolerances[3];

        std::string CalculateResistance(int, int, int, int);
};

Resistor::Resistor() {
        // Black, Brown, Red, Orange, Yellow, Green, Blue, Violet, Gray, White
        for (int i = 0; i < 10; i++)
            Bands[i] = i;

        for (int x = 0; x < 10; x++) {
            for (int y = 0.01; y < 10000000; y *= 10)
                Multipliers[x] = y;
        }

        // Gold, Silver, None
        for (int x = 0; x < 3; x++) {
            for (int y = 5; y < 20; y *= 2)
                Tolerances[x] = y;
        }
}

std::string Resistor::CalculateResistance(int Digit1, int Digit2, int Multiplier, int Tolerance) {
    Convert convert;
    std::string Additive = convert.ToString(Digit1) + convert.ToString(Digit2);

    double y = convert.ToInt32(Additive) * Multiplier;

    std::string z = "";

    if (y >= 0 && y < 999) {
        z = convert.ToString(y) + "Ohm +- " + convert.ToString(Tolerances[Tolerance]);
        return z;
    }

    else if (y > 999 && y < 999999) {
        y /= 1000;

        z = convert.ToString(y) + "K Ohm +- " + convert.ToString(Tolerances[Tolerance]);
        return z;
    }

    else if (y > 999999 && y < 999999999) {
        y /= 1000000;

        z = convert.ToString(y) + "M Ohm +- " + convert.ToString(Tolerances[Tolerance]);
        return z;
    }

    return "error 0: result was out of range.\n";
}

// Convert.h
#include <sstream>
#include <string>

using namespace std;

class Convert {
public:
    bool IsInt32(string);
    int ToInt32(string);
    string ToString(int);
};

    bool Convert::IsInt32(string s) {
        string hyphen = "-";

        if (s[0] == hyphen[0])
            s.erase(0, 1);

        for (int i = 0; i < (int)s.size(); i++)
            if (isdigit(s[i] == 0)) return false;

        return true;
    }

    string Convert::ToString(int i) {
        stringstream s;
        s << i;

        return s.str();
    }

    int Convert::ToInt32(string s) {
        stringstream i;
        int returnVal;

        if (IsInt32(s)) {
            i << s;
            i >> returnVal;
            return returnVal;
        }

        else return -1;
    }

All help is appreciated,
Jamie

NathanOliver 429 Veteran Poster Featured Poster · Answer 5 · 2012-07-02T20:57:34+00:00

Your multiplier array and your code to populate it is the problem. The array is of type int but you are trying to store a double into it. This will just cause a truncation problem for storing the values. The main issue is in your for loop on line 61. You set y to .01 which the compiler will make equal to 0 for an int data type. Since y is zero and you are multiplying it by 10 you will always get zero and have an infinite loop. I would suggest you change the type of the array you are using and you will also need to rewrite the code to fill the array. For filling the array I would do something like this

// in class body
Double Multipliers[10];
//...

// in constructor
Multipliers[0] = .01;
for (int i = 1; i < 10; i++)
    Multipliers[i] = Multipliers[i – 1] * 10;
//…

'string' to 'int' and 'int' to 'string'? Please Help!?

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