Programming Forums > Application Development > C++

Mcoy · Mar 1st, 2006, 9:10 PM

Is a statement like:

a = bob[fred[2]];

valide in c++?(Bob and Fred are two different arrays.)

I know that something like

(Toggle Plain Text)

a = bob[bob[2]];

is valid but a program of mine crashes when I combine two different arrays like I've shown.

Jimbo · Mar 1st, 2006, 9:59 PM

if fred[2] is a valid index of bob[], then it should work.

(Toggle Plain Text)

#include <iostream>

int main()
{
	int bob[] = {2, 3, 4, 5, 6};
	int fred[] = {0, -1, 4, 17, 44};
	std::cout << bob[fred[2]] << std::endl; // outputs 6
	return 0;
}

Mcoy · Mar 2nd, 2006, 6:42 PM

Thanks, I guess I could have figured it out by trying code like that, but I wanted to go to bed by the time I came to that problem :o .
'fred[2]' was indeed a valid index of 'bob[]', but it still crashed.
For some reason filling fred with zero's fixed the problem.

DaWei · Mar 2nd, 2006, 7:25 PM

If 'fred [2]' isn't initialized with a known value, it's accidental value might very easily represent an index not within the bounds of Bob (or any other array). Seg fault. Barf in cuffs. All that bad chit.

Mar 1st, 2006, 9:10 PM	#1
Mcoy Newbie Join Date: Mar 2006 Posts: 20 Rep Power: 0	Getting values of (non-dynamic) arrays... Is a statement like: (Toggle Plain Text) a = bob[fred[2]]; a = bob[fred[2]]; valide in c++?(Bob and Fred are two different arrays.) I know that something like (Toggle Plain Text) a = bob[bob[2]]; a = bob[bob[2]]; is valid but a program of mine crashes when I combine two different arrays like I've shown.

Mar 1st, 2006, 9:59 PM	#2
Jimbo Battle Programmer Join Date: Feb 2006 Location: Bellevue, WA, USA Posts: 751 Rep Power: 3	if fred[2] is a valid index of bob[], then it should work. (Toggle Plain Text) #include <iostream> int main() { int bob[] = {2, 3, 4, 5, 6}; int fred[] = {0, -1, 4, 17, 44}; std::cout << bob[fred[2]] << std::endl; // outputs 6 return 0; } #include <iostream> int main() { int bob[] = {2, 3, 4, 5, 6}; int fred[] = {0, -1, 4, 17, 44}; std::cout << bob[fred[2]] << std::endl; // outputs 6 return 0; }

Mar 2nd, 2006, 7:25 PM	#4
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	If 'fred [2]' isn't initialized with a known value, it's accidental value might very easily represent an index not within the bounds of Bob (or any other array). Seg fault. Barf in cuffs. All that bad chit. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

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Mar 2nd, 2006, 6:42 PM	#3
Mcoy Newbie Join Date: Mar 2006 Posts: 20 Rep Power: 0	Thanks, I guess I could have figured it out by trying code like that, but I wanted to go to bed by the time I came to that problem :o . 'fred[2]' was indeed a valid index of 'bob[]', but it still crashed. For some reason filling fred with zero's fixed the problem.

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Programming Forums > Application Development > C++

Getting values of (non-dynamic) arrays...