std::string depreciated ?

[MintDropz]

i have three files: 1: main 2: math functions 3: header
when i compile (g++ Linux Mint Rebecca) them I get the following error: 'string' is not a member of 'std' \ int getPosInt(std::string);

i assume that means that the string function is not in the standard (std) library? if true where is it?

main

#include <iostream>
#include "myMathFunctions.h"

using namespace std;

int main(){
    int radius = getPosInt("Enter a positive integer for the radius of a circle: ");
    double aCircle = areaOfCircle(radius);
    double vSphere = volOfSphere(radius);

    cout << "The area of a circle with radius of " << radius << " is: " <<  aCircle << endl;
    cout << "The area of a sphere with the radius of " << radius << " is: " << vSphere << endl;    

    return 0;
}

functions

#include <cmath>
#include "myMathFunctions.h"
using namespace std;

// - get a positive integer value from the user and return that value
int getPosInt(string msg){
    int num = 0;
    do{
        cout << msg;
        cin >> num;
    }while(num <= 0);
    return num;
}

// - calculate the area of a circle based on a radius.
// - (Area) A = π r2
double areaOfCircle(int r){
    return (PI * pow(r,2));
}

header

#ifndef MYMATHFUNCTIONS_H_
#define MYMATHFUNCTIONS_H_

const double PI = 3.14159;

int getPosInt(std::string);
double areaOfCircle(int);
double volOfSphere(int);

#endif 

[MintDropz]

also, if i put this into one source file and remove 'std::' from the getPosInt function it compiles fine.

[Disch]

If you're using std::string, you need to #include <string>

[TwilightSpectre]

The reason it worked for if you put it all in one file is that <iostream> does define string. However, it doesn't necessarily define any of the functions used with strings, so its always better to just include <string> when dealing with that type.

[MintDropz]

im confused on how these files pass ?_? am i to use #include <iostream> on every source file that uses in/output stream? i thought that since i declared it in main its declared through out the rest of the program?.

also, is there a certain order files should be sent to the compiler? Does the main function file have to come before rest? i compile this in terminal:
g++ project.cpp myMathFunctions.cpp myMathfunctions.h -o project

thanks for the help.

[MiiNiPaa]

am i to use #include <iostream> on every source file that uses in/output stream?

Yes. Each compilation unit (source file) is compiled independendtly from others. So you must include all headers your header/implementatin file uses. If you use std::string, include <string>. If you use cin, include <iostream>, etc.

is there a certain order files should be sent to the compiler?

For compiling, no. For linking, some compilers, gcc for example, does depend on library order.

[MintDropz]

thanks MiiNiPaa!
two more questions , should the header file also include headers used in it? for example, in my header file i should include #include <string>

second question, does #include <iostream> contain the string definition in it? im guessing it does because i normally dont include the string header but am still able to declare variables as strings.

[MiiNiPaa]

should the header file also include headers used in it?

Yes. But it is a good idea to think if it is really needed. Forward declaration might suffice if only pointer/reference to class is passed as parameter/declared as member.

does #include <iostream> contain the string definition in it?

No. It does not. Standard does not list std::string as something contained in <iostream>. However some internals might include parts of the <string> header. But it is not required and you should not rely on that behavior. At least one alternative STL implementation does includes basic_string definition, but does not define std::string/wstring/etc. type aliases in <iostream>. libstdc++ AFAIR defines type aliases, but does not include any non_member functions like std::to_string

In short you should always include headers containing something you use directly and do not rely on undocumented and nonmandatory behavior.

[MintDropz]

thanks for you explanations and time. i appreciated it.