[C++ help] Why is this being executed twice?

Frostbite130 · **Posted:** Wed Jul 18, 2012 9:40 am

// Project 10 - More Loops.cpp : main project file.

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

using namespace std;


int forLoop()
{
   for(int x = 1; x++ <= 100; cout << "FOR!?\n");
   return 0;
}

int whileLoop()
{
   int x = 1;
   while (x++ < 100)
   {
      cout << "WHILE!!!\n";
   }

   return 5;
}

int doLoop()
{
   int x = 0;
   do(cout << "Doo doo\n");
      while (x++ <= 10);
   
      return 9001;
}

int ifCompact()
{
   int a = 9;
   int b = 11;

   (a >= b) ? cout << "Hello!\n" : cout << "Bye\n"; //?: = if true, do this, if not : do this

   return 2 * 13;
   
}


int main()
{
   forLoop();
   int x = forLoop();
   cout << x << endl;

   whileLoop();
   int a = whileLoop();
   cout << a << endl << endl;

   doLoop();
   int z = doLoop();
   cout << z << endl << endl;

   ifCompact();
   int b = ifCompact();
   cout << b << endl << endl;
   
    
   cout << "Press any key to exit.";
   char z;
   cin >> z;
   return 0;
}

Trying to learn c++ and I'm at this point where I'm learning about different kinds of loops.

In the main function where I call ifCompact() it should say "Hello" if the statement is true, and "Bye!" if the statement is false. I've looked over the whole thing and I can't figure out why when I compile+run it, "Bye!" gets said twice as if that function is being called twice, but I only called it once in main().

Any pros help a newb out?

using microsoft vc++
windows 7 x64

MistaLee · **Joined:** Sat Jun 02, 2012 1:33 am **Location:** zone 6

Frostbite130 wrote:

"Bye!" gets said twice as if that function is being called twice, but I only called it once in main().

look alive there buddy... youre calling each function twice.
each of your calls looks like this...

ifCompact();//Call One
int b = ifCompact();//Call Two

you also have an issue with declaring the variable Z twice.

Frostbite130 · **Posted:** Wed Jul 18, 2012 1:07 pm

I see. Thanks. I guess i didn't realize that that was calling it again. But if thats the case why didnt the other functions get called twice as well?

Or maybe i just dont notice them getting called twice because there's a lot more output.

How would i go about adding the return value of those functions to variables without calling them?

Please forgive my newbness. This is day 2 for me.

MistaLee · **Joined:** Sat Jun 02, 2012 1:33 am **Location:** zone 6

Frostbite130 » Wed Jul 18, 2012 7:07 am wrote:

How would i go about adding the return value of those functions to variables without calling them?

int sum=0+5+9001+26;

oh wait. I misread....the answer is: You dont. If you want to sore a return value in a variable, you have to call the function so it can return the value.

Think of it like this, maybe it will help. Suppose you have a function doLoop() that just returns the value 9001. Every time you call doLoop(), you can think of it as 9001.

that is to say,
int a=doLoop();
is exactly the same as
int a=9001;

or

Code: Select all

int a = doLoop()>>24|(doLoop() << 8 ) & 0x00FF0000|(doLoop() >> 8 ) & 0x0000FF00|doLoop()<<24;
//is exactly the same as 
int a = 9001>>24|(9001 << 8 ) & 0x00FF0000|(9001 >> 8 ) & 0x0000FF00|9001<<24;

steav · **Joined:** Tue Jan 01, 2002 1:00 am

Sitenote:

For beginners it's very important to get "friends" with debugging quickly in order to solve such problems.

Set a breakpoint at the beginning of the code and see what it does step by step, learn to step into / over functions, use conditional breakpoints etc. By doing this you'll learn how the code "thinks" and how to find the reasons for issues.

Micke · **Joined:** Thu Jul 26, 2001 1:00 am **Location:** Sweden

steav » 19 Jul 2012 08:20 wrote:

Sitenote:

For beginners it's very important to get "friends" with debugging quickly in order to solve such problems.

Set a breakpoint at the beginning of the code and see what it does step by step, learn to step into / over functions, use conditional breakpoints etc. By doing this you'll learn how the code "thinks" and how to find the reasons for issues.

+1. I would say that knowing how to debug code is more important that knowing how to write it in the first place

And the visual studio debugger is very beginner friendly in my opinion.

K_OS · **Joined:** Tue Oct 12, 2004 6:13 pm **Location:** Germany

Also trash the book you are using. Every single loop you have written there is like buttsex (and i am not fan of butt sex...)

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// nevver do this, ugly piece of shit
// for(int x = 1; x++ <= 100; cout << "FOR!?\n");
// instead:
for (int x=1; x<=100; ++x) {
  cout << "for" << endl;
}

and even then you might want to change x -> i and count from 0 to <100 instead of 1 to <=100

E: and does this do-while loop even compile? oO

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   do(cout << "Doo doo\n");
      while (x++ <= 10);

it should be

Code: Select all

do {
  cout << "doo doo" << endl;
} while (x++ <= 10);

(note again that <= is misleading. in this case the last iteration is with x = 11)

MistaLee · **Joined:** Sat Jun 02, 2012 1:33 am **Location:** zone 6

K_OS » Thu Jul 19, 2012 5:54 am wrote:

Also trash the book you are using. Every single loop you have written there is like buttsex (and i am not fan of butt sex...)

E: and does this do-while loop even compile? oO

lol come on man, look alive. of course it compiles and runs just fine. its a single line so no need for curlies.

and the for loop, even if it looks like an abortion is fine too. but I would have used the "goes to" operator instead.

Code: Select all

//for x equals ten: as x goes to 0, print FOR!?
for(int x = 10; x  --> 0; cout << "FOR!?\n");

ETA:
I do agree though he should get a new book. these shortcuts are something you should learn once you already know how to code. I almost regret posting the "goes to" operator.
Almost.

K_OS · **Joined:** Tue Oct 12, 2004 6:13 pm **Location:** Germany

you are right. it actually compiles - even though every single implication of the indentation is wrong. (foremost: do is not a function that is being called like do(..) ; ) It should at least be

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do
  cout << "doo" << endl;
while (x++ <= 10);

even without curly braces. (so might as well include them to avoid problems in the future - especially since he is just starting to learn the language)

Micke · **Joined:** Thu Jul 26, 2001 1:00 am **Location:** Sweden

Of course it compiles. A compiler doesn't care about whitespace or indentation or extra parenthesis.

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do(some_statement);

is the same thing as

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do
(some_statement);

which is the same as

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do
   some_statement;

Indentation was just invented so programmers could have yet another way to confuse the ones trying to read the code.

I've seen so many people say that this would print "x = 6" because they just look at the indentation instead of the actual code.

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int x = 0;
for(int i = 0; i < 5; ++i)
   x++,
x++;
cout << "x = " << x << endl;

Skatebro · **Joined:** Mon Dec 02, 2002 8:55 pm

Code: Select all

for(int x = 1; x++ <= 100; cout << "FOR!?\n");

that is fucking terrible. please never code like that again

Blizzhackers

[C++ help] Why is this being executed twice?

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