Learning cplusplus, trubles!

[kunimitzu]

So i am learning c++ and i found a rather strange problem.
been re-reading my code several times to try and find whats the problem, without any luck i have to say.
Now i came here to see if someone could help me out, and explain this for me, as i know it will be a problem down the road even if it is not now.



this is how a test run looks like and if you read through it you will see that in firstname "one" is missing.
why does it remove the first characters until a space ? if the name were "one" it would output " "

here is my code

#include <iostream>#include <string>


using namespace std;


int main()
{
    int numbervariable;
    cout << "How Old Are You?\n I am : ";
    cin >> numbervariable;


//char give single character and string allows several, but does not allow spaces
    string firstname;
    cout << "What is your first name?\n My first name is : ";
    cin >> firstname;
//for some reason this will blank out the first part of the name; "tom = " "
    getline ( cin, firstname, '\n' );
//without it the application will skip all cin and rush through the process if the name entered is "first middle" or "first - middle" form.
    string lastname;
    cout << "What is your last name?\n My last name is : ";
    cin >> lastname;
    string charactervariable = firstname + " " + lastname;


    double decvar;
    cout << "How much do you weight in kilograms?\nI weight : ";
    cin >> decvar;


    cout << "Your name is : " << charactervariable << ".\nYou are : " << numbervariable << " Years old." << "\nYour weight is : " << decvar << "kg." << "\n \n";


    int numplus = 0;
    cout << ++numplus;


    return 0;
}

Thanks in advance.
- kun

[xalcon]

You cannot use the stream syntax with cin in this szenario. When streaming into cin the space character is used as a delimiter.
The reason you get just the leading parts after a space is simple:
You read the first word until the first occuring space. Then you use getline() to read the full line, but the carret is already set to the second word (due to the cin stream behavior), overriding the first word in firstname with the leading part.

In order to get you program working, you need to replace all "cin >> string" calls with getline(). To read into other types then string (like int or double) you need to read the remaining stuff fromt he line (the newline character, for example). I've created a "garbage" string for this purpose, but there are many ways to solve this problem.
Just an working example:

#include <iostream>
#include <string>


using namespace std;


int main()
{
	string garbage;
    int numbervariable;
    cout << "How Old Are You?\n I am : ";
    cin >> numbervariable;
	// we only got the number, but there is still a newline character we need to skip
	getline(cin, garbage);


    string firstname;
    cout << "What is your first name?\n My first name is : ";
    getline (cin, firstname, '\n');


    string lastname;
    cout << "What is your last name?\n My last name is : ";
    getline (cin, lastname, '\n');
    string charactervariable = firstname + " " + lastname;


	double decvar;
    cout << "How much do you weight in kilograms?\nI weight : ";
	cin >> decvar;
	// same as for the numbervariable above, read the newline character
	getline(cin, garbage);


    cout << "Your name is : " << charactervariable << ".\nYou are : " << numbervariable << " Years old." << "\nYour weight is : " << decvar << "kg." << "\n \n";


    int numplus = 0;
    cout << ++numplus;


    return 0;
}

output:

How Old Are You?
I am : 123
What is your first name?
My first name is : Abc Defg
What is your last name?
My last name is : van long name
How much do you weight in kilograms?
I weight : 1337
Your name is : Abc Defg van long name.
You are : 123 Years old.
Your weight is : 1337kg.

1

[kunimitzu]

thanks, especially for explaining as well as giving example.
now i am able to continue my learning book, did not want go ahead without understanding everything in the previous chapter.
i am sure i will have more simple, like this, and advanced problems later in my learning.

[kunimitzu]

now i made another simple tutorial program, this time it ran as expected and everything worked fine, however it gave me 2 compile warnings.



so my question here would be, are these warnings something i should pay attention to ?
should i bother fixing it, rather than ignoring it when the program work as expected.

also note; the two lines were "numbercheck" is used, i found to be necessary for the program to run as intended,
otherwise, without me declaring it outside "while 1" it would get an error and not run.


EDIT: Solved these warnings by moving the whole "if bool, else" part into the proper "if password" section, which also allowed me to remove the first declaration of "numbercheck"

also found that the first code, in img, would give me some problems if i navigated deep enough into the program.

so for others who want to learn, the picture is how its not done.

here is the working code for this program.

#include <iostream>
#include <string>


using namespace std;


int main()
{
    string password = "Test";
    string userinput;
    cout << "What is the correct password ? \n Password : ";
    getline( cin, userinput, '\n' );


    while (1)
        {


            if (userinput == password)
                {
                    cout << "\nCorrect password was entered \n";
                    return 0;
                    cin.get();
                }


            else if (userinput == "Hacked")
                {
                    int number;
                    cout << "\nPassword Hacked ! \n Type a number to enter : ";
                    cin >> number;
                    bool numbercheck = number == 2;




                if ( numbercheck )
                    {
                        cout << "\nCorrect number was entered ! \n";
                        cin.get();
                        return 0;
                    }
                else
                    {
                        cout << "\nWrong number ! Try again ! \n";
                        cin.get();
                    }


                }


            else
                {
                        cout << "\nWrong password was entered \nTry again : ";
                        getline( cin, userinput, '\n');


                }
        }
}

[stoneharry]

Warnings are exactly what they are - warnings. The compiler and/or your IDE is telling you this might be an issue.

In your screen shot it looks like one variable is not given an initial value, this will error if you try to use it and it doesn't have a value. Im sure your book will go into more details about them later.

Posted from phone so hard to answer.

[kunimitzu]

solved it by doing some more trails and error, but thank you anyway.
also as u said, the book went more into warnings and compilers and such.

Edit: Solved next problem.

-Kun