Programming BrainScratch

rohan2kool · 02-03-2006, 01:23 PM

Well, anybody can do normal programming.... Everybody understands the printf() function... But... here are a series of questions that will force every developer to think.. The answer might be obvious... but tax your brains hard for it...

Q1) Under practical conditions, will the following loop break(or stop) anytime:

Code:

for(int i=0; i<-1; i++) {
      //Some code here
}

Try this... Answers are to be backed up by reasons. Right answers, but wrong reasons are not the right solutions

Enjoy...

kenni · 02-03-2006, 06:42 PM

Not really sure, i've never come across the "<-"

for(int i=0; i<-1; i++) {
//Some code here
}

rohan2kool · 02-04-2006, 04:26 AM

it's not <- it is <(-1), it's minus 1.

So, you can call it:

for(int i=0; i< (-1); i++) {
//some code here
}

compuXP · 02-05-2006, 03:44 AM

Yeah that would just keep looping...

pairbrother · 02-05-2006, 09:47 AM

under practical conditions, it is an infinite loop.
under impractical conitions, the loop can break if we change the value of i to negative (like -2) inside the code

or put a break

rohan2kool · 02-05-2006, 01:27 PM

Well... supposing the value of 'i' is not changed at all and there is no 'break' statement or any sort of code that may cause the program to crash and thereby cause the program to terminate. Suppose it to be this:

for(int i=0; i< (-1); i++) {
printf("My name is Rohan Prabhu");
}

I repeat my question, Q1) Under practical conditions, will the following loop break(or stop) anytime?

pairbrother · 02-05-2006, 03:27 PM

under very practical conditions i think it will not...

but then since u r askin this q, probably it will stop sometime..lol

umm...in C max value of int is 32767 after that if we increment it, it wiil become -32768, which will satisfy the condition and hence the loop will stop!?

rohan2kool · 02-06-2006, 09:08 AM

Quote:

Originally Posted by pairbrother

under very practical conditions i think it will not...

but then since u r askin this q, probably it will stop sometime..lol

umm...in C max value of int is 32767 after that if we increment it, it wiil become -32768, which will satisfy the condition and hence the loop will stop!?

Your answer is correct, but the reasoning is slightly wrong. Do check the note below

Excellent d00d. Your answer is absolutely correct. When the number reaches 32767 (in C or 2147483647 in 32-bit numbers) the binary would appear as:

0111111111111111b

Adding 1 to it would make the number:

1000000000000000b

which is actually 32768 in unsigned numbers... but in signed numbers it is 0. Actually, it is -0. Then on adding another number to it, it then becomes:

1000000000000001b

which in unsigned numbers is 32769, but in signed number it is -1. Similarly after another iteration, it is converted to -2 (signed) and hence the loop terminates.

Correction: According to your reasoning, the number aftere 32767 turns to -32767. It is not so. It happens only in signed numbers, but due to the binary system not working on the signed principle, it increments the number according to the binary rule, but interprets it as a binary number and signs it and uses it as an integer. And it does not become -32767, it becomes 0, then -1, then -2 and so on...

I hope you liked this part of programming brainScratch. Watch out for the next question...

-Rohan Prabhu

pairbrother · 02-06-2006, 05:09 PM

infact
i ran this code in java...

Code:

public class testt {
	public static void main(String[] args) {
		System.out.println("entering loop...");
		for(int i=0; i<-1; i++) {
			  System.out.println("i: " + i);
		}
		System.out.println("out of loop");
	}
}

and the output is

Code:

entering loop...
out of loop

that means, not even once does it enter in the loop

now y is that so?

Code:

for(int i=0; i<-1; i++)

i=0 initializes i to 0
then it checks the condition i < -1 thatis 0 < -1 which gives the result as false and so the loop breaks......

thts wht i cud understand..:p

xpertcoder · 02-22-2006, 01:05 PM

Quote:

Originally Posted by pairbrother

infact
i ran this code in java...

Code:

public class testt {
	public static void main(String[] args) {
		System.out.println("entering loop...");
		for(int i=0; i<-1; i++) {
			  System.out.println("i: " + i);
		}
		System.out.println("out of loop");
	}
}

and the output is

Code:

entering loop...
out of loop

that means, not even once does it enter in the loop

now y is that so?

Code:

for(int i=0; i<-1; i++)

i=0 initializes i to 0
then it checks the condition i < -1 thatis 0 < -1 which gives the result as false and so the loop breaks......

thts wht i cud understand..:p

I completely agree with what pairbrother has stated ... the logic is perfect and the reasoning is provided with the proper proof.
for(int i=0; i<-1; i++) literally means

int i = 0 --> Initialization of intereger variable "i" as zer0
i <-1 --> until the value of i is less than -1 ( which "0" is defintely not)
i++ --> means Increment i by 1

As the condition of i<-1 itself is not satisfied inthe 2nd step the loop is discontinued.

Brain Scratch

rohan2kool · 08-25-2006, 04:52 PM

oopssy... i screwed up an excellent question.. the loop should be:

Code:

for(int i=0;i>=0;i++) {
   //The code here
}

sorry for the goof up guys

compuXP · 08-25-2006, 11:16 PM

Lol, nice save after 6 months

No wonder I got confused!

rohan2kool · 08-28-2006, 04:59 PM

just didn't notice it for long... just wanted to read some of my creations... so pondered over the last post and found out the mistake

sorry guys

02-03-2006, 01:23 PM	#1
rohan2kool Member Join Date: Dec 2005 Posts: 132	Programming BrainScratch Well, anybody can do normal programming.... Everybody understands the printf() function... But... here are a series of questions that will force every developer to think.. The answer might be obvious... but tax your brains hard for it... Q1) Under practical conditions, will the following loop break(or stop) anytime: Code: for(int i=0; i<-1; i++) { //Some code here } Try this... Answers are to be backed up by reasons. Right answers, but wrong reasons are not the right solutions Enjoy... __________________ Eat healthy, Stay Fit, Die Anyway. --==-- If there is a man who knows everything about women, there is a Windows distribution without bugs. Last edited 02-03-2006 at 01:25 PM.

02-03-2006, 06:42 PM	#2
kenni Registered Member Join Date: Dec 2005 Posts: 1,543	Re: Programming BrainScratch Not really sure, i've never come across the "<-" for(int i=0; i<-1; i++) { //Some code here } __________________ Wanna thank someone? Give 'em a rep. More info.

02-04-2006, 04:26 AM	#3
rohan2kool Member Join Date: Dec 2005 Posts: 132	Re: Programming BrainScratch it's not <- it is <(-1), it's minus 1. So, you can call it: for(int i=0; i< (-1); i++) { //some code here } __________________ Eat healthy, Stay Fit, Die Anyway. --==-- If there is a man who knows everything about women, there is a Windows distribution without bugs.

02-05-2006, 03:44 AM	#4
compuXP Retired Member Join Date: Dec 2005 Posts: 139	Re: Programming BrainScratch Yeah that would just keep looping... __________________ Retired Moderator/Member/Friend/Helper - it was great working with all of you!

02-05-2006, 09:47 AM	#5
pairbrother Regular Member Join Date: Dec 2005 Location: India Posts: 222	Re: Programming BrainScratch under practical conditions, it is an infinite loop. under impractical conitions, the loop can break if we change the value of i to negative (like -2) inside the code or put a break __________________ Amrita Rao \| YVIR Directory \| Cricket World Cup 2007

02-05-2006, 01:27 PM	#6
rohan2kool Member Join Date: Dec 2005 Posts: 132	Re: Programming BrainScratch Well... supposing the value of 'i' is not changed at all and there is no 'break' statement or any sort of code that may cause the program to crash and thereby cause the program to terminate. Suppose it to be this: for(int i=0; i< (-1); i++) { printf("My name is Rohan Prabhu"); } I repeat my question, Q1) Under practical conditions, will the following loop break(or stop) anytime? __________________ Eat healthy, Stay Fit, Die Anyway. --==-- If there is a man who knows everything about women, there is a Windows distribution without bugs.

02-05-2006, 03:27 PM	#7
pairbrother Regular Member Join Date: Dec 2005 Location: India Posts: 222	Re: Programming BrainScratch under very practical conditions i think it will not... but then since u r askin this q, probably it will stop sometime..lol umm...in C max value of int is 32767 after that if we increment it, it wiil become -32768, which will satisfy the condition and hence the loop will stop!? __________________ Amrita Rao \| YVIR Directory \| Cricket World Cup 2007

02-06-2006, 05:09 PM	#9
pairbrother Regular Member Join Date: Dec 2005 Location: India Posts: 222	Re: Programming BrainScratch infact i ran this code in java... Code: public class testt { public static void main(String[] args) { System.out.println("entering loop..."); for(int i=0; i<-1; i++) { System.out.println("i: " + i); } System.out.println("out of loop"); } } and the output is Code: entering loop... out of loop that means, not even once does it enter in the loop now y is that so? Code: for(int i=0; i<-1; i++) i=0 initializes i to 0 then it checks the condition i < -1 thatis 0 < -1 which gives the result as false and so the loop breaks...... thts wht i cud understand..:p __________________ Amrita Rao \| YVIR Directory \| Cricket World Cup 2007

08-25-2006, 04:52 PM	#11
rohan2kool Member Join Date: Dec 2005 Posts: 132	Re: Programming BrainScratch oopssy... i screwed up an excellent question.. the loop should be: Code: for(int i=0;i>=0;i++) { //The code here } sorry for the goof up guys __________________ Eat healthy, Stay Fit, Die Anyway. --==-- If there is a man who knows everything about women, there is a Windows distribution without bugs.

08-25-2006, 11:16 PM	#12
compuXP Retired Member Join Date: Dec 2005 Posts: 139	Re: Programming BrainScratch Lol, nice save after 6 months No wonder I got confused! __________________ Retired Moderator/Member/Friend/Helper - it was great working with all of you!

08-28-2006, 04:59 PM	#13
rohan2kool Member Join Date: Dec 2005 Posts: 132	Re: Programming BrainScratch just didn't notice it for long... just wanted to read some of my creations... so pondered over the last post and found out the mistake sorry guys __________________ Eat healthy, Stay Fit, Die Anyway. --==-- If there is a man who knows everything about women, there is a Windows distribution without bugs.

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