Thread: Function Loop problem

a program with a function printmsg() that has a parameter n. the function prints the messag "hello world" n time
tried making one. not looping. what is problem

Code:

#include<iostream.h>
#include<conio.h>
int getsum(int a);
void printmsg();
main()
{
    clrscr();
    int n;
    cout<<"Enter a number : ";
    cin>>n;
    do
    {
        printmsg();
        cout<<getsum(n);
    }
    while(getsum(n)<=1);
    getch();
    return(0);
}
int getsum(int a)
{
    int sum;
    do
    {
        sum=a--;
        return sum;
    }
    while(a<=1);
}
void printmsg()
{
    cout<<"hello world";
}

Originally Posted by Rodaxoleaux

I have more questions than answering the problem. How is that compiling? At all?

iostream.h shouldn't exist.
#include <iostream> would be the correct nomenclature.

main() has no type. You never even include std::cout or std::cin, so that shouldn't let you do anything.

I suggest getting a new compiler first o3o.

Yes it compiles.main has no type,but by default it is equivalent to write main() to int main(void).iostream can be written like this.Fot the std the only explanation is that conio.h may contain a using namespace std.(however i do not know what conio.h is)

im using turbo c++ 3.0
im a noob at programming and my teacher taught me this way of writing a program through C++.

#include<iostream.h> works for some reason in my compiler
i dont know about your std::cout or std::cin but my cout and cin work which my teacher taught me works.

Originally Posted by std10093

Of course #include<iostream.h> works!!!!But we use to write it as #include<iostream>...the .h reminds me of C.
Now about the loop,do you understand what i said above?

EDIT -> Some warnings should the compiler shows to you though

uhmm, i get that return sum returns the variable, thats all i get. all the others are just confusing to me.

function getsum does not do anything special.It returns immediately variable sum(in essence a).The -- is done at a after the assignment of a to sum,so it does not affect at all.So if i input 10,getsum will return 10,and 10 is not <= of 1,so false statement at line 16,so no looping!

Originally Posted by std10093

function getsum does not do anything special.It returns immediately variable sum(in essence a).The -- is done at a after the assignment of a to sum,so it does not affect at all.So if i input 10,getsum will return 10,and 10 is not <= of 1,so false statement at line 16,so no looping!

i think i get the uhm -- thing.
here's a sample

Code:

a--
sum=a
return sum;

so i must use -- first before assigning it to sum? correct?.

You have to understand that the location of ++ and -- is significant.
Check this example and try to explain why the output is what it is.

Code:

#include <iostream>
using namespace std;
 

main()
{
    int a=7;
    cout<<a++<<endl;
    cout<<a<<endl;
    cout<<--a<<endl;
    cout<<a<<endl;
    
    return 0;
}

If you can not,just state it and i am going to explain it to you right away!

whats endl?

i did a major revision of my code
i dont know if this is correct or not. plss help with the do while.

Code:

#include<iostream.h>
#include<conio.h>
int prnmsg(int a);
main()
{
    clrscr();
    int n;
    cout<<"Enter a number : ";
    cin>>n;
    do
    {
        cout<<"hello world"<<prnmsg(n);
    }
    while(prnmsg(n)<=1);
    getch();
    return(0);
}
int prnmsg(int a)
{
    int sum;
    do
    {
        a--;
        sum=a;
        return sum;
    }
    while(a<=1);
}

endl says to end the line at the ouput(like you hitted enter)..Nothing special

As for the code you wrote,it is a bit better,but not good enough.The goal is to print "hello word" as many times as the n.Correct?Your program does not do that

Originally Posted by langamer101

Code:

#include<iostream.h>
#include<conio.h>
int prnmsg(int a);
main()
{
    clrscr();
    int n;
    cout<<"Enter a number : ";
    cin>>n;
    do
    {
        cout<<"hello world"<<prnmsg(n);
    }
    while(prnmsg(n)<=1);
    getch();
    return(0);
}
int prnmsg(int a)
{
    int sum;
    do
    {
        a--;
        sum=a;
        return sum;
    }
    while(a<=1);
}

Let's see what does this code do..
Until line 9 is pretty clear.
Line 10 we reach the do while structure.We enter the loop and the message is printed.
Then ,in line 14,the prnmsg function is called.Inside this function we decrease the a(which has the value of n) by one in line 23.
Then we assign a to sum at line 24.
Then ,in line 25, the function will be terminated(!) and sum will be returned.So the do-while structure at lines 21-27 is useless,because at line 21 we are sure that our code will enter the loop,but in line 25 the function will be terminated,so the statement at line 27 with the while will not be checked at all.No matter if a<=1(line 27) <-the function is not going to reach this point,so the loop inside the function will never be executed!!
Then after the function returns sum we come back at line 14 and check if prnmsg(n)<=1 which is equivalent to sum<=1.This will be true only if the user inputs something that is smaller or equal to 1,so actually <= is wrong.

You could use something like this
(read the e.g. i have on a post above with --)

Code:

#include<iostream>
using namespace std;

int main(void)
{
 
    int n;
    cout<<"Enter a number : ";
    cin>>n;
    do
    {
        cout<<"hello world"<<endl;
    }
    while(--n);
    
    return(0);
}

or with less lines

Code:

 
#include<iostream>
using namespace std;
main()
{
 
    int n;
    cout<<"Enter a number : ";
    cin>>n;
    while(n--)
    {
        cout<<"hello world"<<endl;
    }
    
    return(0);
}

Originally Posted by langamer101

. plss help with the do while.

Why don't you try a for structure instead of do while.A for structure is used when we know the excact times of loops that are going to be made.It is written like this

Code:

...
for(int i=0 ; i<=10 ; i++)
{
      cout<<"i am into the loop and it feels good"<<endl;
}
...

What this line does is this.Declare an integer i and set it to zero(int i=0).
Then it is going to check if the statement is true or false(i<=10).If it is true the loop will be executed,if it false it will skip the loop and continue into the rest of the code.
In case we enter the loop when the loop reaches to it's end and so we go back to line 2,where the line of for lies.There we are going to increase i by one factor(i++).
So how many times will this loop be executed?Eleven!At the last loop i is 10,it enters the loop,prints the message at line 4 and then at the end of the loop it is increased by one,so it becomes 11.So when we go back at line 2,we check if i<=10,but i is 11,so false statement,so we skip the loop and go on at line 6.

So when should i use a for structure instead of a while or a do-while structure?
for structure is used when we know the excact numbers the loop will be executed.At your program we want to print hello world n times.You do not how many times the message will be printed(that is to say,how many times the loop is going to be executed),until the user inputs a value for n.So,you do not know if it is going to be 10 times or 3 or whatever.But you know that it is going to be printed n times,and that is enough for you to decide to use a for statement
So what we should write is this

Code:

#include <iostream>
using namespace std;

main()
{
 
    int n;
    cout<<"Enter a number : ";
    cin>>n;
    for(int i=0; i<n ; i++)
    {
        cout<<"hello world"<<endl;
    }
    
    return(0);
}

Originally Posted by jimblumberg

Actually in C++ default return types are not permitted, it shouldn't compile with a standard conforming compiler. The <iostream.h> header file is a pre-standard header file that did not use the standard namespace. This means that the OP is using an ancient compiler and desperately needs to find a more modern compiler. Also the <conio.h> header is a non-standard DOS/Windows include file and it doesn't know anything about the standard namespace.

Jim

i think this is an ANCIENT (turbo c++ 3.0) compiler which i heard from my teacher or some online forums whatnot. why does my school use ancient compilers ahhhhhhhh.