I am wrecking my brain trying to figure this. Please bear with me as I'm only in my forth week into learning C++.
The code below works fine when having all the code just in the main()
int main()
{
cout << setfill('0') << setw(1) << hundreds << setw(1) << tens
<< setw(1) << units << "\n";
system("PAUSE");
return 0;
}
However I've been asked to make it work so that the code is split, but I can't seem to do it. My attempt is below. If someone could send me on the right track that would be great. Please bare in mind that we haven't learnt anything to complex so it shouldn't be hard.
int main()
{
cout << "The encrypted number is: " << recomposedEncryptedNumber() << "\n";
system("PAUSE");
return (0);
}
int recomposedEncryptedNumber()
{
return setfill('0') << setw(1) << hundreds << setw(1) << tens << setw(1) << units;
}
the expression cout << stuff has cout as return value so you need to do the same in your function:
std::ostream& recomposedEncryptedNumber()
{
return cout << setfill('0') << setw(1) << hundreds << setw(1) << tens << setw(1) << units;
}
Your initial code combines a lot on a single line. I'm breaking it apart for explanation:
int main()
{
cout // cout is "console output" -- i.e. how you print to the screen
<< setfill('0') // This is the operation "cout << setfill('0')"
// which creates a modifier "setfill", passes it to cout,
// and now you've "taught" cout to use '0' as the fill
// character.
// Importantly, "cout << setfill('0')" returns cout...
<< setw(1) // This is the operation "cout << setw(1)".
// It's applying the "<< setw(1)" to the return of the
// previous command. This is also a special modifier,
// and again, this returns 'cout'.
<< hundreds // Now you're finally printing something, because this
// is doing "cout << hundreds"
<< setw(1)
<< tens
<< setw(1)
<< units
<< "\n";
system("PAUSE");
return 0;
}
Importantly, every operation in that long line is cout << {something}, and the result of the << operation is the cout again -- which is why you can chain the statements together.
Knowing that, you should now be able to see why this fails:
int recomposedEncryptedNumber()
{
return
setfill('0') // This gives you the setfill modifier.
// -- but that's _not_ cout.
<< setw(1) // "setfill << setw"?? Not what you want at all.
// You want "cout << setfill" and "cout << setw".
<< hundreds << setw(1) << tens << setw(1) << units;
}
You have many options on how to proceed. You could do something like this:
int main() {
cout << "The encrypted number is: ";
printRecomposedEncryptedNumber();
cout << "\n";
}
These are three separate statements. Now printRecomposedEncryptedNumber can print your details to cout directly, and return void (i.e. not return anything).
If you want to do it inline:
int main() {
cout << "The encrypted number is: " << recomposedEncryptedNumber() << "\n";
}
Then your recomposedEncryptedNumber must return something that can be given to cout. Since you're trying to do some special formatting, you don't want to use int -- cout will just display the int the way it wants to. So you should use a string. Then your function can do whatever formatting it wants, and return the properly formatted string:
string recomposedEncryptedNumber(int hundreds, int tens, int units)
{
std::ostringstream msg; // 'o' is for output
// 'string' is because we're building a string
// 'stream' is because this uses streaming methods
// i.e. 'ostringstream' lets us build a string,
// by using streaming mechanisms.
// Same stream machinations you were doing before, just with 'msg'
// instead of 'cout'
msg << setfill('0') << setw(1) << hundreds << setw(1) << tens << setw(1) << units;
return msg.str(); // return the string we've built.
}
Lastly, in order for your function to access hundreds, tens, units, the function must be given those variables (i.e. the variables must be passed into the function as parameters).
Welcome to C++!
Did you declare your prototype before main? for example. I do not have more time to explain but here is how you would do it
#include <iostream>
#include <iomanip>
using namespace std;
void recomposedEncryptedNumber(int hun, int tens, int units);
int main()
{
int hun = 1;
int tens = 1;
int units = 1;
cout << "The encrypted number is: " << "\n";
recomposedEncryptedNumber(hun,tens,units);
system("PAUSE");
return (0);
}
void recomposedEncryptedNumber(int hun, int tens, int units)
{
cout << setfill('0') << setw(1) << hun << setw(1) << tens << setw(1) << units;
}`
cout print on the standard output, you're trying to mix 2 types and that's why it doesn't work.
Try it :
std::string recomposedEncryptedNumber()
{
std::string str;
concat(str,setfill('0'));
concat(str,setw(1));
...
return str;
}
Well,
thats how I would implement what I think you need:
#include <iostream>
#include <iomanip>
using namespace std;
class EncryptedNumber
{
public:
EncryptedNumber( unsigned h, unsigned t, unsigned u )
: hundreds( h ),
tens( t ),
units( u )
{}
protected:
unsigned hundreds,
tens,
units;
friend std::ostream & operator << ( std::ostream& outs, const EncryptedNumber& en );
};
std::ostream & operator << ( std::ostream& outs, const EncryptedNumber& en )
{
outs << setfill( '0' ) << setw( 1 ) << en.hundreds
<< setw( 1 ) << en.tens
<< setw( 1 ) << en.units;
return outs;
}
int main()
{
EncryptedNumber en( 1, 2, 3 );
cout << "The encrypted number is: " << en << "\n";
system("PAUSE");
return (0);
}
Of course it is a quick solution and I haven't created getter/setter methods, didn't split the concept from implementantion and nothing useful inside EncryptedNumber.
The point is that code will look far more elegant and mantainable this way.
Please tell me if you want a more detailed explanation.
Related
I need to write ints from the right and strings from the left into a single line and have them line up properly (view output below the code).
Basically I just need a way to write a table only using iostream and iomanip and change the allingment from right for ints to left for strings and back.
Other tips are also appreciated :)
#include <iostream>
#include <iomanip>
using namespace std;
class foo
{
public:
int i;
std::string s;
int j;
foo(int i1,std::string s1,int j1) : i(i1), s(s1),j(j1) {};
};
int main()
{
foo f1(1, "abc",50);
foo f2(100, "abcde",60);
cout << resetiosflags(ios::adjustfield);
cout << setiosflags(ios::right);
cout << setw(6) << "i" << setw(15) << "s" << setw(15) << "j"<<endl;
cout << setw(8) << f1.i << setw(15)
<< resetiosflags(ios::adjustfield) << setiosflags(ios::left) << f1.s <<setw(5)
<< resetiosflags(ios::adjustfield) << setiosflags(ios::right) << setw(15) << f1.j << endl;
cout << setw(8) << f2.i << setw(15)
<< resetiosflags(ios::adjustfield) << setiosflags(ios::left) << f2.s <<setw(5
<< resetiosflags(ios::adjustfield) << setiosflags(ios::right) << setw(15) << f2.j << endl;
/*i s j
1abc 50
100abcde 60*/
return 0;
}
This is the output:
i s j
1abc 50
100abcde 60
And this is what i need:
i s j
1 abc 50
100 abcde 60
Using left and right in the same line isn't a problem. It looks like the issue you have is not allowing for space after the first value. It looks like the setw(5) may have been for that, but since there's nothing printed after it there's no effect. I used 7 to match the 15 total used for the string width.
Maybe something like this would work? Probably best to extract the magic numbers into constants so you can adjust all of them easily in one place. You could also wrap this in an operator<< to contain all the formatting code in one place.
The first line headings offset one to the left looks weird to me, but it matches your example and is easy to adjust if necessary.
#include <iostream>
#include <iomanip>
using namespace std;
class foo
{
public:
int i;
std::string s;
int j;
foo(int i1, std::string s1, int j1) : i(i1), s(s1), j(j1)
{};
};
int main()
{
foo f1(1, "abc", 50);
foo f2(100, "abcde", 60);
cout
<< right << setw(7) << "i" << setw(7) << ' '
<< left << setw(15) << "s"
<< right << "j"
<< endl;
cout
<< right << setw(8) << f1.i << setw(7) << ' '
<< left << setw(15) << f1.s
<< right << f1.j
<< endl;
cout
<< right << setw(8) << f2.i << setw(7) << ' '
<< left << setw(15) << f2.s
<< right << f2.j
<< endl;
return 0;
}
Output:
i s j
1 abc 50
100 abcde 60
Okay so I have a calorie calculator that is supposed to be separated into the five functions including main seen below. My issue is that I get a compiler error because the variables from the inputNumber function and calculateCalories function cannot be read by any of the other functions once they are obtained. I am not allowed to use Global variables. There must be something I am missing to be able to read the variables within the main function then output them into the other functions to get the proper output. Any help would be appreciated.
Here is the code as it stands:
#include <iostream>
#include <string>
#include <iomanip>
using namespace std;
int main()
{
int Lbs, hourr, hourW, hourWe, hourb;
double calBad, calRun, calWal, calWei;
string name;
cout << "Welcome to Megan McCracken's Workout Calculator!" << endl;
cout << endl;
cout << "Please enter your name: ";
getline(cin, name);
inputNumber(Lbs, hourr, hourW, hourWe, hourb);
calculateCalories(Lbs,hourr,hourb,hourW,hourWe,calBad,calRun,calWal,calWei);
displayHeadings(name);
displayLine(hourr,hourb,hourW,hourWe,calBad,calRun,calWal,calWei);
system("pause");
return 0;
}
int inputNumber(int Lbs, int hourr, int hourb, int hourW, int hourWe)
{
cout << "Please enter your weight: ";
cin >> Lbs;
return Lbs;
cout << "Please enter the minutes spent playing badminton: ";
cin >> hourb;
return hourb;
cout << "Please enter the minutes spent running: ";
cin >> hourr;
return hourr;
cout << "Please enter the minutes spent walking: ";
cin >> hourW;
return hourW;
cout << "Please enter the minutes spent lifting weights: ";
cin >> hourWe;
return hourWe;
cout << endl;
}
double calculateCalories(int Lbs, int hourW, int hourb, int hourr, int hourWe, double calBad, double calRun, double calWal, double calWei)
{
const double Badburn = .044, Runburn = .087, Walkb = .036, Weightb = .042;
double calBad, calRun, calWal, calWei;
calBad = (Badburn * Lbs) * hourb;
calRun = (Runburn * Lbs) * hourr;
calWal = (Walkb * Lbs) * hourW;
calWei = (Weightb * Lbs) * hourWe;
return calBad;
return calRun;
return calWal;
return calWei;
}
void displayHeadings(string name)
{
cout << "Here are the results for " << name << ": " << endl;
cout << endl;
cout << "Activity" << right << setw(18) << "Time" << right << setw(10) << "Calories" << endl;
cout << "--------------------------------------" << endl;
}
void displayLine(int hourb,int hourr, int hourW, int hourWe, double calBad, double calRun, double calWal, double calWei)
{
int HB, MB, HR, MR, HW, MW, HWE, MWE, Hour, Min;
double Calorie;
HB = (hourb / 60);
MB = (hourb % 60);
HR = (hourr / 60);
MR = (hourr % 60);
HW = (hourW / 60);
MW = (hourW % 60);
HWE = (hourWe / 60);
MWE = (hourWe % 60);
Calorie = calBad + calRun + calWal + calWei;
Hour = (hourb + hourr + hourW + hourWe) / 60;
Min = (hourb + hourr + hourW + hourWe) % 60;
cout << "Badminton" << right << setw(14) << HB << ":" << setfill('0') << setw(2) << MB << setfill(' ') << right << setw(10) << setprecision(3) << fixed << showpoint << calBad << endl;
cout << resetiosflags(ios::fixed | ios::showpoint);
cout << "Running" << right << setw(16) << HR << ":" << setfill('0') << setw(2) << MR << setfill(' ') << right << setw(10) << setprecision(3) << fixed << showpoint << calRun << endl;
cout << resetiosflags(ios::fixed | ios::showpoint);
cout << "Walking" << right << setw(16) << HW << ":" << setfill('0') << setw(2) << MW << setfill(' ') << right << setw(10) << setprecision(3) << fixed << showpoint << calWal << endl;
cout << resetiosflags(ios::fixed | ios::showpoint);
cout << "Weights" << right << setw(16) << HWE << ":" << setfill('0') << setw(2) << MWE << setfill(' ') << right << setw(10) << setprecision(3) << fixed << showpoint << calWei << endl;
cout << "--------------------------------------" << endl;
cout << resetiosflags(ios::fixed | ios::showpoint);
cout << "Totals" << right << setw(17) << Hour << ":" << setfill('0') << setw(2) << Min << setfill(' ') << right << setw(10) << setprecision(3) << fixed << showpoint << Calorie << endl;
cout << endl;
}
If you want to modify passed-in variables within a function in C++, you should be passing them in by reference (default is by value, meaning you get a copy of the variable which is effectively thrown away when the function exits).
So, by way of example:
void xyzzy (int plugh) { plugh = 42; }
int main() {
int twisty = 7;
xyzzy (twisty);
cout << twisty << '\n';
return 0;
}
will output 7 because twisty was passed by value and changes to it within the function will not be echoed back to the caller.
However, if you pass by reference with:
void xyzzy (int &plugh) { plugh = 42; }
// ^
// This does the trick.
then you'll find it outputs 42 as desired.
For your particular case, you want to look at the variables in the argument list of inputNumber:
int inputNumber(int Lbs, int hourr, int hourb, int hourW, int hourWe)
Any of these that you want echoed back to the caller (and that looks like all of them from a cursory glance) should be pass by reference rather than pass by value.
You should also look into calculateCalories as well, since that is doing the same thing. Keep in mind that only the ones you want to change and echo back to the caller need to be pass-by-reference. So that's only the ones starting with cal.
And, since you're using the pass-by-reference to modify the variables, there's absolutely no reason to return anything from that function so it can be specified as void calculateCalories ... and the return statements removed (in any case, only the first return would have actually done anything, the others would have been unreachable code).
If you haven't yet got to the point where you can use references in your classwork (as seems to be indicated by one of your comments), you can do what C coders have been doing for decades, emulating pass-by-reference with pointers. In terms of the simplified example above, that would mean modifying the function to receive a pointer to the item you want changed, changing what it points to, and calling it with the address of the variable to be changed:
void xyzzy (int *pPlugh) { *pPlugh = 42; }
int main() {
int twisty = 7;
xyzzy (&twisty);
cout << twisty << '\n';
return 0;
}
However, it's a poor substitute for the real thing and, if your educator is trying to teach you that, it's the same as if they're getting you to use printf/scanf rather than cout/cin for user I/O: it's certainly possible in C++ since the language includes legacy C stuff, but it's not really teaching you the C++ way.
People who claim to be C++ developers but really code in C using a C++ compiler, are a rather strange breed that I like to call C+ developers - they've never really embraced the language properly. The sooner people put aside the legacy stuff, the better they'll be as C++ developers.
Pass the variables by references. Then the functions will be able to edit them.
Your other solution (not so much of a good idea but still working) is to create a struct/class and make the functions return it.
P.S. Your code won't work if the functions are in this order unless you add their signatures in the beginning:
int main();
int inputNumber(int,int,int,int,int);
//and so on
In input number, you can not use 'return' to return each value - it will do the first return statement.
In C++ you can use pass by reference so that values assigned to the variables will be passed back up.
In this case, via the input variables would be inputNumber so use '&' to denote the vaiables are references:
void inputNumber(int &Lbs, int &hourr, int &hourb, int &hourW, int &hourWe)
{
.
.
.
}
Similar idea for calculateCalories, get rid of the returns:
void calculateCalories(int Lbs, int hourW, int hourb, int hourr, int hourWe, double &calBad, double &calRun, double &calWal, double &calWei)
{
.
.
}
Note that we are only bothering to pass to reference for the variables that we will be passing back.
Closed. This question needs debugging details. It is not currently accepting answers.
Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 8 years ago.
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I'm making a USD to MXN converter and I want to have it work both ways. The if statement works (tryed cout << "test"; and it worked) but it wont work when I replace it with the goto statement.
#include "stdafx.h"
#include <cstdlib>
#include <iostream>
using namespace std;
int main(int argc, char *argv[])
{
int user;
int u, m;
cout << "US/MXN Converter" << endl;
cout << "1 US = 12.99 MXN (6/12/2014)" << endl;
cout << endl;
cout << "What Way to convert" << endl;
cout << "[1] US to MXN" << endl;
cout << "[2] MXN to US" << endl;
cout << "Selection: ";
cin >> user;
if (user == 1)
{
goto USTMXN;
}
else
{
goto MXNTUS;
}
USTMXN:
cout << "Enter the amount of US Dollars to Convert" << endl;
cout << "Amount: ";
cin >> u;
m = u * 12.99;
cout << endl;
cout << "MXN Pesos: " << m << endl;
goto END;
MXNTUS:
int mm, uu;
cout << "Enter the amount of Pesos to Convert" << endl;
cout << "Amount: ";
cin >> mm;
uu = mm / 12.99;
cout << endl;
cout << "US Dollars: " << m << endl;
goto END;
END:
system("PAUSE");
return EXIT_SUCCESS;
}
One of the most fundamental things we have to do as programmers is to learn to break problems into smaller problems. You are actually running into a whole series of problems.
I'm going to show you how to solve your problem. You may want to book mark this answer, because I'm pre-empting some problems you're going to run into a few steps down the line and preparing you - if you pay attention - to solve them on your own ;)
Let's start by stripping down your code.
Live demo here: http://ideone.com/aUCtmM
#include <iostream>
int main()
{
std::cout << "Enter a number: ";
int i;
std::cin >> i;
std::cout << "Enter a second number: ";
int j;
std::cin >> j;
std::cout << "i = '" << i << "', j = '" << j << "'\n";
}
What are we checking here? We're checking that we can ask the user two questions. That works fine.
Next is your use of goto, which I strongly recommend you do not use. It would be better to use a function. I'll demonstrate with your goto case here first:
#include <iostream>
int main()
{
int choice;
std::cout << "Enter choice 1 or 2: ";
std::cin >> choice;
if ( choice == 1 )
goto CHOSE1;
else if ( choice == 2 )
goto CHOSE2;
else {
std::cout << "It was a simple enough question!\n";
goto END;
}
CHOSE1:
std::cout << "Chose 1\n";
goto END;
CHOSE2:
std::cout << "Chose 2\n";
goto END;
END:
std::cout << "Here we are at end\n";
}
live demo: http://ideone.com/1ElcV8
So goto isn't the problem.
That leaves your use of variables. You've really mixed things up nastily by having a second set of variables (mm, uu). Not only do you not need to have these, you're doing something very naughty in that these variables only exist inside one scope and not the other. You can "get away" with this but it will come back to haunt you later on.
The difference in your two main streams of code is the variable names. The second conversion case looks like this:
MXNTUS:
int mm, uu;
cout << "Enter the amount of Pesos to Convert" << endl;
cout << "Amount: ";
cin >> mm;
uu = mm / 12.99;
cout << endl;
cout << "US Dollars: " << m << endl;
goto END;
The problem here is that you have - accidentally - used the variable "m" in your output. It's what we call uninitialized.
cout << "US Dollars: " << m << endl;
That m in the middle should be mm.
Your compiler should actually be warning you about this. If it's not, and you're just setting out learning, you should figure out how to increase the compiler warning level.
It would be better to make a function to do the conversions; you could make one function for each direction, but I've made a function that handles both cases:
#include <iostream>
static const double US_TO_MXN = 12.99;
static const char DATA_DATE[] = "6/12/2014";
void convert(const char* from, const char* to, double exchange)
{
std::cout << "Enter the number of " << from << " to convert to " << to << ".\n"
"Amount: ";
int original;
std::cin >> original;
std::cout << to << ": " << (original * exchange) << '\n';
}
int main() // this is valid since C++2003
{
std::cout << "US/MXN Converter\n"
"1 US = " << US_TO_MXN << " MXN (" << DATA_DATE << ")\n"
"\n";
int choice = 0;
// Here's a better demonstration of goto
GET_CHOICE:
std::cout << "Which conversion do you want to perform?\n"
"[1] US to MXN\n"
"[2] MXN to US\n"
"Selection: ";
std::cin >> choice;
if (choice == 1)
convert("US Dollars", "Pesos", US_TO_MXN);
else if (choice == 2)
convert("Pesos", "US Dollars", 1 / US_TO_MXN);
else {
std::cerr << "Invalid choice. Please try again.\n";
goto GET_CHOICE;
}
// this also serves to demonstrate that goto is bad because
// it's not obvious from the above that you have a loop.
}
ideone live demo: http://ideone.com/qwpRtQ
With this, we could go on to clean things up a whole bunch and extend it:
#include <iostream>
using std::cin;
using std::cout;
static const double USD_TO_MXN = 12.99;
static const double GBP_TO_MXN = 22.03;
static const char DATA_DATE[] = "6/12/2014";
void convert(const char* from, const char* to, double exchange)
{
cout << "Enter the number of " << from << " to convert to " << to << ".\n"
"Amount: ";
int original;
cin >> original;
cout << '\n' << original << ' ' << from << " gives " << int(original * exchange) << ' ' << to << ".\n";
}
int main() // this is valid since C++2003
{
cout << "Foreign Currency Converter\n"
"1 USD = " << USD_TO_MXN << " MXN (" << DATA_DATE << ")\n"
"1 GBP = " << GBP_TO_MXN << " MXN (" << DATA_DATE << ")\n"
"\n";
for ( ; ; ) { // continuous loop
cout << "Which conversion do you want to perform?\n"
"[1] USD to MXN\n"
"[2] MXN to USD\n"
"[3] GBP to MXN\n"
"[4] MXN to GBP\n"
"[0] Quit\n"
"Selection: ";
int choice = -1;
cin >> choice;
cout << '\n';
switch (choice) {
case 0:
return 0; // return from main
case 1:
convert("US Dollars", "Pesos", USD_TO_MXN);
break;
case 2:
convert("Pesos", "US Dollars", 1 / USD_TO_MXN);
break;
case 3:
convert("British Pounds", "Pesos", GBP_TO_MXN);
break;
case 4:
convert("Pesos", "British Pounds", 1 / GBP_TO_MXN);
break;
default:
cout << "Invalid selection. Try again.\n";
}
}
}
http://ideone.com/iCXrpU
There is a lot more room for improvement with this, but I hope it helps you on your way.
---- EDIT ----
A late tip: It appears you're using visual studio, based on the system("PAUSE"). Instead of having to add to your code, just use Debug -> Start Without Debugging or press Ctrl-F5. It'll do the pause for you automatically :)
---- EDIT 2 ----
Some "how did you do that" points.
cout << '\n' << original << ' ' << from << " gives " << int(original * exchange) << ' ' << to << ".\n";
I very carefully didn't do the using namespace std;, when you start using more C++ that directive will become the bane of your existence. It's best not to get used to it, and only let yourself start using it later on when you're a lot more comfortable with C++ programming and more importantly debugging odd compile errors.
But by adding using std::cout and using std::cin I saved myself a lot of typing without creating a minefield of function/variable names that I have to avoid.,
What does the line do then:
cout << '\n' << original << ' ' << from << " gives " << int(original * exchange) << ' ' << to << ".\n";
The '\n' is a single character, a carriage return. It's more efficient to do this than std::endl because std::endl has to go poke the output system and force a write; it's not just the end-of-line character, it actually terminates the line, if you will.
int(original * exchange)
This is a C++ feature that confuses C programmers. I'm actually creating a "temporary" integer with the result of original * exchange as parameters.
int i = 0;
int i(0);
both are equivalent, and some programmers suggest it is better to get into the habit of using the second mechanism so that you understand what happens when you later run into something called the "most vexing parse" :)
convert("Pesos", "British Pounds", 1 / GBP_TO_MXN)
The 1 / x "invert"s the value.
cout << "Foreign Currency Converter\n"
"1 USD = " << USD_TO_MXN << " MXN (" << DATA_DATE << ")\n"
"1 GBP = " << GBP_TO_MXN << " MXN (" << DATA_DATE << ")\n"
"\n";
This is likely to be confusing. I'm mixing metaphors with this and I'm a little ashamed of it, but it reads nicely. Again, employ the concept of breaking problems up into smaller problems.
cout << "Hello " "world" << '\n';
(note: "\n" and '\n' are different: "\n" is actually a string whereas '\n' is literally just the carriage return character)
This would print
Hello world
When C++ sees two string literals separated by whitespace (or comments) like this, it concatenates them, so it actually passes "Hello world" to cout.
So you could rewrite this chunk of code as
cout << "Foreign Currency Converter\n1 USD = ";
cout << USD_TO_MXN;
cout << " MXN (";
cout << DATA_DATE;
cout << ")\n1 GBP = ";
cout << GBP_TO_MXN;
cout << " MXN (";
cout << DATA_DATE;
cout << ")\n\n";
The << is what we call "semantic sugar". When you write
cout << i;
the compiler is translating this into
cout.operator<<(i);
This odd-looking function call returns cout. So when you write
cout << i << j;
it's actually translating it to
(cout.operator<<(i)).operator<<(j);
the expression in parenthesis (cout.operator<<(i)) returns cout, so it becomes
cout.operator<<(i); // get cout back to use on next line
cout.operator<<(j);
Main's fingerprint
int main()
int main(int argc, const char* argv[])
Both are legal. The first is perfectly acceptable C or C++. The second is only useful when you plan to capture "command line arguments".
Lastly, in main
return 0;
Remember that main is specified as returning int. The C and C++ standards make a special case for main that say its the only function where it's not an error not to return anything, in which case the program's "exit code" could be anything.
Usually its best to return something. In C and C++ "0" is considered "false" while anything else (anything that is not-zero) is "true". So C and C++ programs have a convention of returning an error code of 0 (false, no error) to indicate the program was successful or exited without problems, or anything else to indicate (e.g. 1, 2 ... 255) as an error.
Using a "return" from main will end the program.
Try to change youre code for sth like this. Using goto label is not recommended.
Main idea of switch statement :
int option;
cin >> option
switch(option)
{
case 1: // executed if option == 1
{
... code to be executed ...
break;
}
case 99: //executed id option == 99
{
... code to be executed
break;
}
default: // if non of above value was passed to option
{
// ...code...
break;
}
}
Its only example.
int main(int argc, char *argv[])
{
int user;
int u, m;
cout << "US/MXN Converter" << endl;
cout << "1 US = 12.99 MXN (6/12/2014)" << endl;
cout << endl;
cout << "What Way to convert" << endl;
cout << "[1] US to MXN" << endl;
cout << "[2] MXN to US" << endl;
cout << "Selection: ";
cin >> user;
switch(user )
{
case 1 :
{
//USTMXN:
cout << "Enter the amount of US Dollars to Convert" << endl;
cout << "Amount: ";
cin >> u;
m = u * 12.99;
cout << endl;
cout << "MXN Pesos: " << m << endl;
break;
}
}
default :
{
//MXNTUS:
int mm, uu;
cout << "Enter the amount of Pesos to Convert" << endl;
cout << "Amount: ";
cin >> mm;
uu = mm / 12.99;
cout << endl;
cout << "US Dollars: " << m << endl;
break;
}
}
system("PAUSE");
return EXIT_SUCCESS;
}
I'm trying to display a text file data into columns using a class structure and getline() function to read through the textfile and the dump the data into a vector class. But it seems that the program didn't even run to my 'while' loop then quitting the program. The textfile is not empty.
Below is my code:
void ScrambleWordGame::displayScoreChart() {
//open file
fstream readScoreChart("ScoreChart.txt");
string line = "";
//vector to store data in
vector<personResult> perResult;
personResult person;
//while file is open, do stuff
if(readScoreChart.is_open())
{
//check through the file
readScoreChart.seekp(0,ios::end);
//get the size of the file's data
size_t size = readScoreChart.tellg();
if(size == 0)
cout << "No results yet. Please TRY to win a game. AT LEAST~" << endl;
else
{
//create the 1st row with 4 column names
cout << left
<< setw(20) << "Player Name "
<< setw(20) << "Winning Time "
<< setw(20) << "No. Of Attempts "
<< setw(20) << "Game Level " << endl;
//fill the second line with dashes(create underline)
cout << setw(70) << setfill('-') << "-" << endl;
//read the file line by line
//push the 1st line data into 'line'
cout << getline(readScoreChart,line);
while(getline(readScoreChart,line))
{
//create stringstream n push in the entire line in
stringstream lineStream(line);
//reads the stringstream and dump the data seperated by delimiter
getline(lineStream,person.playerName,':');
getline(lineStream,person.winningTime,':');
getline(lineStream,person.noOfAttempts,':');
getline(lineStream,person.gameLvl);
//sort the results based on their timing
//sort(perResult.begin(),perResult.end(),pRes);
//display the results
cout << left
<< setfill(' ')
<< setw(25) << person.playerName
<< setw(22) << person.winningTime
<< setw(17) << person.noOfAttempts
<< setw(16) << person.gameLvl
<< endl;
}
}
}
readScoreChart.close();
}
Edit: Example of the TextFile
Joel:3:1:1
Mary:5:2:2
John:25:3:1
Your file pointer is at the end of the file after your first seek. You need to reposition it to the beginning of the file.
if(size == 0)
{
cout << "No results yet. Please TRY to win a game. AT LEAST~" << endl;
}
else
{
readScoreChart.seekp(0,ios::begin);
// all you other stuff
}
You need to seek back to the beginning of the file to be able to read. Better still, just don't seek to the end in the first place.
I'd re-structure the code a bit -- write an operator>> to read a record from a file, and an operator<< to write a record to a file.
class person {
std::string name;
std::string winning_time;
std::string num_attempts;
std::string level;
public:
bool operator<(person const &other) const {
return std::stoi(winning_time) < std::stoi(other.winning_time);
}
friend std::istream &operator>>(std::istream &in, person &p) {
std::string buffer;
std::getline(in, buffer);
std::istringstream is(buffer);
std::getline(is,p.name,':');
std::getline(is,p.winning_time,':');
std::getline(is,p.num_attempts,':');
std::getline(is,p.level);
return in;
}
friend std::ostream &operator<<(std::ostream &os, person const &p) {
return os << std::setw(25) << p.name
<< std::setw(22) << p.winning_time
<< std::setw(17) << p.num_attempts
<< std::setw(16) << p.level;
}
};
With those in place, the rest gets quite a bit simpler:
void show_header(std::ostream &os) {
cout << left
<< setw(20) << "Player Name "
<< setw(20) << "Winning Time "
<< setw(20) << "No. Of Attempts "
<< setw(20) << "Game Level " << "\n";
std::cout << std::string(70, '-');
}
void game::displayScoreChart(){
std::ifstream in("ScoreChart.txt");
// read the data:
std::vector<person> people{std::istream_iterator<person>(in),
std::istream_iterator<person>()};
if (people.empty()) {
std::cout << "No scores yet."
return;
}
// sort it by winning time:
std::sort(people.begin(), people.end());
show_header(std::cout);
// display it:
for (auto const &p : people)
std::cout << p << "\n";
return 0;
}
As a simple replacement if you don't have a C++11 compiler, an stoi can be written something like this:
int stoi(std::string in) {
return strtol(in.c_str(), NULL, 10);
}
I want to write a little program which should be used in supermarkets. everything is fictitious and it's only for learning purposes.
However, The tool generate a new data for every new article. in the data there are 2 lines, the name and the prise.
The data is named as the article number of the product. So the user enter a articlenumber and the tool looks for a data with this number, if it found it, it reads the 2 lines and initiates the variables.
But for some reasons it does not convert and copy the strings correctly.
here is the part which loads the data.
int ware::load()
{
string inhalt;
cout << "please insert article number" << endl;
cin >> articlenumber;
productname.open(articlenumber, ios::in);
if (!productname.is_open())
{
cout << "can't find the product." << endl;
return 1;
}
if (productname.is_open())
{
while (!productname.eof())
{
getline(productname, inhalt);
strcpy(name,inhalt.c_str());
getline(productname, inhalt);
price = atoi (inhalt.c_str());
cout << inhalt << endl;
}
warenname.close();
}
cout << endl << endl <<
"number: " << inhalt <<
" preis: " << price <<
" name: " << name <<
endl << endl; //this is a test and will be deleted in the final
}
hope you can help me!
Here is the class:
class ware{
private:
char articlenumber[9];
char name[20];
int price;
fstream warennamefstream;
ifstream warenname;
public:
void newarticle(); //this to make a new product.
void scan(); //this to 'scan' a product (entering the article number ;D)
void output(); //later to output a bill
int load(); //load the datas.
};
hope everything is fine now.
First, you have a using namespace std; somewhere in your code. This occasionally leads to subtle bugs. Delete it. ( Using std Namespace )
int ware::load()
{
string inhalt;
cout << "please insert article number" << endl;
cin >> articlenumber;
The type of articlenumber is incorrect. Declare it std::string, not char[]. ( What is a buffer overflow and how do I cause one? )
productname.open(articlenumber, ios::in);
There is no reason to have an ifstream lying around waiting to be used. Also, there is no point in providing ios::in -- it is the default. Just use the one-argument form of the ifstream constructor.
if (!productname.is_open())
{
cout << "can't find the product." << endl;
return 1;
}
Don't bother checking to see if the file opened. Your users don't care if the file was present or not, they care whether the file was present AND you retrieved the essential data.
if (productname.is_open())
{
while (!productname.eof())
{
getline(productname, inhalt);
strcpy(name,inhalt.c_str());
getline(productname, inhalt);
price = atoi (inhalt.c_str());
cout << inhalt << endl;
}
warenname.close();
}
This loop is just wrong.
Never invoke eof(). It doesn't do what you think it does, and will cause bugs.
Why is this a loop? Aren't there only two lines in the file?
There is no point in calling close. Just let the file close when the istream goes out of scope.
Why is warename different than productname?
Don't store your data in char[]. This is the 21st century. Use std::string.
.
cout << endl << endl <<
"number: " << inhalt <<
" preis: " << price <<
" name: " << name <<
endl << endl; //this is a test and will be deleted in the final
Never use endl when you mean to say '\n'. Each of those endl manipulators invokes flush, which can be very expensive. ( What is the C++ iostream endl fiasco? )
You forgot to return a value.
Try this instead:
int ware::load()
{
// This declaration should be local
std::string articlenumber;
cout << "please insert article number" << endl;
cin >> articlenumber;
// This declaration should be local
std::ifstream productname(articlenumber.c_str());
// These declarations can be class members:
std::string name;
int price;
std::string number;
if(getline(productname, name) &&
productname>>price &&
productname>>number)
{
cout << "\n\n" <<
"number: " number <<
" preis: " << price <<
" name: " << name <<
"\n\n"; //this is a test and will be deleted in the final
return 0;
} else {
cout << "can't find the product." << endl;
return 1;
}
}