why is the "cout" function not working in functions?

Question

0.00/5 (No votes)

See more:

hello everyone,
i'm a beginner and have a small problem regarding a code.
the compiler flags an error saying:-

VB

error C2065: 'cout' : undeclared identifier

here is the code

C++

char downer(char[13])
{
cout<<"hello";
}

using namespace std;

int main()
{
char ocean[13];
puts(" please enter the name of the ocean ");
cin>>ocean;
downer(ocean);
}

please help me to deal with this error.

here is a link to the whole code( just in case you want to reffer to it )
link[]

Posted 1-Sep-13 5:00am

A.U.K

Updated 1-Sep-13 5:22am

v2

Add a Solution

Comments

Sergey Alexandrovich Kryukov 1-Sep-13 11:40am

Wrong. The problem has nothing to do with "functions".
—SA

Philippe Mori 2-Sep-13 11:24am

If you write a using statement, then it should be done before the function that need it.

4 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Sergey Alexandrovich Kryukov · Accepted Answer · 2013-09-01T05:46:00

Solution 2

The problem has nothing to do with "functions".
You should use #include <iostream> and also using namespace std:

C++

#include <iostream>
using namespace std;

//...

void SomeFunction(/* ... */)
{
    cout << "Now working!";
    //... 
}

//...

You also need to learn how namespaces work, and probably a lot more.

[EDIT #1]

I can see the changes in the question. Still, it need fixes. The code lacks #include <iostream>. Now, the code won't compile, because downer does not return anything. So, change return type to void. And parameter of this function is pointless, removed it from function definition and the call. (In future, you may need char* parameter, to pass a string without specification of its length; usually, in C and C++, null-terminated string is used.)

That's all.

[EDIT #2]

As Stefan_Lang pointed out, there is are considerable benefits of not using "using namespace". You can use fully-qualified names instead. This way excludes name clash, and — very important in this very case — promotes understanding of what really goes on.

The output line shown above will look like

C++

std::cout << "Working without using namespace";

Good luck,

—SA

Posted 1-Sep-13 5:46am

Sergey Alexandrovich Kryukov

Updated 2-Sep-13 4:56am

v7

Comments

AlwaysLearningNewStuff 1-Sep-13 16:28pm

He did use it, see the link in his post at the bottom.

Sergey Alexandrovich Kryukov 1-Sep-13 21:35pm

Who cares what's written there? This is all what's required. This "using" appeared after I put this answer.
—SA

AlwaysLearningNewStuff 1-Sep-13 23:21pm

I believe you, but the link at the bottom of the page shows his full code, and it is slightly different, and included both statements( include<iostream> and using namespace std).

I thought that it was his original one, but maybe he edited it in the meantime, according to your instructions.

Never mind.

Regards.

Sergey Alexandrovich Kryukov 2-Sep-13 0:33am

Not exactly. The code still wrong, and it would not compile. Look, this is lame stuff which does not deserve mentioning, but I answered how to make the code work, please see after [EDIT].
—SA

AlwaysLearningNewStuff 2-Sep-13 1:07am

You are right, there is no need to discuss about this.

The OP has enough answers to correct his solution, and that is what the purpose of this section is all about.

Maybe there was a misunderstanding from my side, since I saw the question later, but there is no need to debate about such a pointless thing.

Thank you for reply, and I apologize for any misunderstanding that might have happened.

Regards.

Stefan_Lang 2-Sep-13 5:14am

While it is a common practive, I wouldn't recommend using 'using namespace' to anyone. You might argue that namespace std is so common that it shouldn't cause problems. But I wouldn't use it even then, if only to not provide a bad precedence.

Personally I prefer adding the namespace prefix at all times as an additional means to comment the origin of the objects and types I use. It's so much easier to read and understand a fully qualified name than looking at a short name and guessing whether or not it is local or part of some namespace. Anyway, I spend much more time thinking than typing, so typing speed is never an argument for me to lower code standards.

Herb Sutter also provided reasons and some examples against 'using' declarations and directives: http://www.gotw.ca/gotw/053.htm

Sergey Alexandrovich Kryukov 2-Sep-13 10:42am

I kind of agree. Even though I see nothing wrong in using "using namespace" in this simple code sample (making little sense anyway, so the goal was only to show why OP failed to use cout), your argument are correct, especially when you dismiss "saving time on typing" "argument". I would prefer saying "it depends", but of course, problems of using (and especially over-using) "using namespace" are apparent.

But of course, for a beginner, it's important to know the fully-qualified naming as the primary way of naming things, and, first of all, promoting understanding of namespaces. So, I added a [EDIT] to my question and credited your comment. And thank you for sharing the link.

—SA

Stefan_Lang 2-Sep-13 10:53am

Indeed, you cannot be too careful in your advice towards a beginner. Thank you for considering my remarks and incorporating them in your solution.

With all those edits there's nothing else I can think of to add - have a 5.

Sergey Alexandrovich Kryukov 2-Sep-13 10:55am

Thank you, Stefan.
—SA

Philippe Mori 2-Sep-13 11:31am

Well, it is a bad practice for header files as it will pollute every files that include that header. For a source file, it can be done on a file by file or even function by function basis as appropriate.

Sergey Alexandrovich Kryukov 2-Sep-13 12:11pm

Of course, thank you for this note. Fortunately, none of us even thought of such a bad practice, but it was nice of you to mention that — I'm sure some would make such a mistake. As to some discreet use of it in CPP (not include) files, as I say, "it depends" approach would be reasonable enough.
—SA

Stefan_Lang 3-Sep-13 2:50am

Absolutely.

In a way, using is even worse than #define, because there is no way to 'unuse' a symbol or namespace. I think you can encapsulate it's use through namespaces, but I never bothered trying or even looking it up since I prefer writing fully classified names anyway.

Sergey Alexandrovich Kryukov 3-Sep-13 12:14pm

Sure. I must say, such attempts to "shortcut" everything is typical for not very good beginners. (Okay, I got it: now I know that I need to use std, so I want to write it once and forget.) Bad way of thinking.

For example, I faced (and down-voted) CodeProject article, where the author developed Visual Studio add-on to "fix" the cases when "using System" is removed, by adding this line automatically to all files. I tried to argue that this is a pure harm, not helpful at all: the files without use of System are usual, and System is no different from other assemblies. The author did not get it...

—SA

A.U.K 7-Sep-13 9:59am

hello bro,
it's me again, i just read all the comments for the soltion:-)
although i din't understand 70% of that stuff since it's of high level,
i do understand that you guys tried to help me in all possible ways in which u can.
thank you for your valuble contribution:-)
so i was actually hoping that we could be friends on FB or G+( that is if you don't mind )
and get to know each other:-)
please let me know:-)

Sergey Alexandrovich Kryukov 7-Sep-13 10:06am

Thank you, but I'm not using those social networks, CodeProject is quite enough.
We will gladly help you. By the way, you should understand 100% of the above, to do development. If you don't, please ask your questions.

Good luck,
—SA

A.U.K 7-Sep-13 10:37am

well, i'm just a beginner and will surely understand them in gradual course of time( since i'm still learning, i will come across those consecpts in near future ).

Sergey Alexandrovich Kryukov 7-Sep-13 12:55pm

That's right, but all what we discussed in this thread is only what's relevant to your question. We really discussed what's the best practice; where to use "using namespace" and where not. Practical considerations could be subtle, but the essence of it is very simple: you either use fully-qualified names (with namespace prefix, like std::cout) or write "using namespace" which gives your something similar to "search path", but that adds a possibility for ambiguity. Besides, when you just look at code, you may not understand where this "cout" comes from...

Basically, that's all...

—SA

AlwaysLearningNewStuff · Accepted Answer · 2013-09-01T10:13:00

I have rewritten your code, so you can see your mistakes.

Before that, a small set of explanations, since I believe, based on your code, that you are familiar with C, so these explanations might help you:

Let us start with your function.

Since you just want to write something to the console, using cout, you do not need the return value ( see the comments in the code, char is changed in void ).

Also, I have changed cout statement to output the ocean string, that you have passed to the function, see the code.

You have passed the string to the function downer in a wrong way, I have changed that too.

Forget about puts, use cout instead, I have changed that in my code too.

Instead of float, I have used double as a type for your variables with decimal points, see the code.

I have added return statement at the very end of the code, this signals that main exited without error.

It seems to me that you know C and try to learn C++. I hope that this code will help you, if you need anything just post a comment, and I will help you.

Finally, the code:

C++

#include<iostream>
     
using namespace std;
   
void downer( char* test) // <-- this is how you pass a string to a function
{
        // endl just tells cout to go to new line, it is like '\n' in C

	cout<<"hello kaka" << endl << test<< endl;
}
     
int main()
{
	char ocean[13]; 

	int boats,fiiden;

        // use double instead of float for decimal numbers

	double poden=11.29387,inden=12.989,atden=10.28172,arden=9.192772;
        
	cout << " this program calculates the number of fish in any specified ocean " << endl;

        // no need for puts, use cout instead

	cout << " please enter the name of the ocean " << endl;
        
	cin >> ocean;
        
	downer( ocean );

        return 0; // this indicates that main exited successfully without errors!
}

OriginalGriff · Accepted Answer · 2013-09-01T05:10:00

Solution 1

Because you forgot to include the header file...
Try:

C++

#include <iostream>

Posted 1-Sep-13 5:10am

OriginalGriff

Updated 1-Sep-13 5:11am

v2

Comments

A.U.K 1-Sep-13 11:35am

hello sir,
i have already included the headeer file,
please check the link to verify :-)

Mohibur Rashid 2-Sep-13 0:41am

either you use std namespace. i.e.
using namespace std;
or
write like this
std::cout<<"whatever";

try to understand c++ namespace

A.U.K 7-Sep-13 9:46am

thank you sir

Ali Elmi · Accepted Answer · 2013-09-01T10:17:00

Solution 4

"cout" uses a library which is called iostream. so you have to use its namespace.

#include <iostream>

Posted 1-Sep-13 10:17am

Ali Elmi

Updated 1-Sep-13 23:15pm

v2

why is the "cout" function not working in functions?

4 solutions

Solution 2

Solution 3

Solution 1

Solution 4

Add your solution here

Preview 0

Existing Members

...or Join us