Need help in Understanding an output problem of C++

Replies

• 

  Sanyam Khurana

  #-Link-Snipped-# and #-Link-Snipped-#
  
  Can you help in this..?
• 

  Kaustubh Katdare

  Tagging #-Link-Snipped-#
• 

  rahul69

  Sanyam Khurana

  #-Link-Snipped-# and #-Link-Snipped-#
  
  Can you help in this..?

  OK , let me answer your questions one by one
  

  So, first of all, is this correct?

  Yes this is technically correct, i.e it will not give any errors.
  Reason being, we can write any statement inside for loop initialisation . We can even leave it empty, see for example:
  

  for(;;;);

  is a valid statement. 😀
  

  and how we judge the output..?

  
  For judging the output, let me explain the working of a for loop in a general manner:
  
  

  1. Initialization condition;
  2. loop(test condition)
  3. {
  4. body statements.....
  5. ...
  6. updation (ie increment etc.);
  7. }

  
  which is written in a for loop as :
  
  for(Initialization; test; updation)
  
  {
  
  body statements...
  
  }
  
  Notice above that initialization statement is executed only once
  
  Now in the code u mentioned, there can be many doubts which u may face as this code uses some tricky concepts as static variable , post increment operator etc, so try solving the output, it will be along the lines of :
  
  38,35,32.... upto 2 .
  
  If u face any problem do mention it, I'll be happy to help 😀
• 

  Sanyam Khurana

  I'm not getting it, what is initialized by the function, how it is updated, and what condition is being checked..??
  
  Please help 😕
• 

  Sanyam Khurana

  Ok, let's take it step by step here
  
  in Initialisation, we have fun(); so, it would return 40 and then in memory it would have value 39 due to post increment, but where is this value returned by the function going to be stored, I mean, we have to store the value in a variable which is returned by the function so as to use it, but here no variable is there..?
• 

  Jeffrey Arulraj

  The fun() returns a value 39 and that is assigned to the control variable of the for loop
  
  I think you can look into the function of return() statement for info #-Link-Snipped-#
• 

  Sanyam Khurana

  Conqueror

  The fun() returns a value 39 and that is assigned to the control variable of the for loop
  
  I think you can look into the function of return() statement for info #-Link-Snipped-#

  Wouldn't it first return the value of num and then decrement it in the memory, due to post decrement operator..?
  
  As in, it would give value of 40 only, but in memory the value would be 39.
  
  Now, whatever value may the function has given, but in order to run the for loop, we must have some initialisation condition and test and update expression as in
  
  

  .
  //some header files
  void main(){
  //assume some code
  for(int i=1;i<10;i++){
  //assume some code 
  }
  }

  Now, whatever value is returned, but shouldn't that be stored in a variable ?
  
  because we have to continuously use it in iteration?
• 

  rahul69

  Sanyam Khurana

  Wouldn't it first return the value of num and then decrement it in the memory, due to post decrement operator..?
  As in, it would give value of 40 only, but in memory the value would be 39.

  Yes u are right 😀.
  

  Sanyam Khurana

  Now, whatever value may the function has given, but in order to run the for loop, we must have some initialisation condition and test and update expression as in
  
  

  .
  //some header files
  void main(){
  //assume some code
  for(int i=1;i<10;i++){
  //assume some code
  }
  }

  Now, whatever value is returned, but shouldn't that be stored in a variable ?
  
  because we have to continuously use it in iteration?

  See, as I told earlier these three expressions viz. initialization, test and update are not mandatory conditions, u may not initialize if u don't want to, same goes for other two, we write these conditions as per the need of our program.
  Lets take each condition one by one:
  
  We test to come out of loop, test means either true (non zero) or false (zero value). Here whenever function will return zero, loop will end, so no need to store it😀.
  
  We update the value so that test condition can be fulfilled, now as the value is changing by means of fun() function. So no need of update too.
  
  And, no need to initialize here as the variable is initialized to 40 in the fun() function.
  Hope it clears your doubts 😀
  -Rahul
• 

  Sanyam Khurana

  rahul69

  Yes u are right 😀.
  
  See, as I told earlier these three expressions viz. initialization, test and update are not mandatory conditions, u may not initialize if u don't want to, same goes for other two, we write these conditions as per the need of our program.
  Lets take each condition one by one:
  
  We test to come out of loop, test means either true (non zero) or false (zero value). Here whenever function will return zero, loop will end, so no need to store it😀.
  
  We update the value so that test condition can be fulfilled, now as the value is changing by means of fun() function. So no need of update too.
  
  And, no need to initialize here as the variable is initialized to 40 in the fun() function.
  Hope it clears your doubts 😀
  -Rahul

  
  
  Yes, I got it, hows it executed, in each iteration, when update expression is executed it call the fun function , again value of num decrements, and then in test condition, it again decrements, and finally when output is given the function is called and value of num is one less than that...
  
  
  Yes, I got it now..
  
  Thanks man..!!! 🎉
• 

  simplycoder

  I think I am slightly late here, but anyways, this was a good example.
• 

  Vishal Sharma

  me too! returned home now 😛
• 

  Sanyam Khurana

  simplycoder

  I think I am slightly late here, but anyways, this was a good example.

  Vishal0203

  me too! returned home now 😛

  Don't get disappointed if I have or someone else have more doubts they will ask you here.. 👍