pointers to multidimensional arrays in C

[Kuciwalker]

I have an assignment to write a program that does a bunch of crap with matrices in C. One thing I have to do is randomize the contents of a matrix. I want to do this by copying random data from memory into the matrix (yes, I know there are other ways, but I'm not using them). So I have to create a pointer to an int[100][100] array, and then use malloc. I've tried declaring this as int temp[100][100]*, but the compiler gives me an error. I don't get an error if I declare it as int * temp[100][100], but I'm not sure if that's a point to a matrix or a matrix of pointers. Moreover, I have to cast malloc to a pointer to an int[100][100], but the compiler doesn't like temp = (int[100][100]*) malloc(40000), either.

[KrazyHorse]

[Whoha]

memory allocation will kick your butt real hard.
use the other ways you bozo.

[Kuciwalker]

NO.

[Kuciwalker]

Originally posted by KrazyHorse

I might as well find out how to do it now, even if it's an inefficient and more difficult way of doing things

[Richelieu]

OMFG! Pointers!!!! NOOOOOOOOOOOOOOOOOO!!!!

[Whoha]

Originally posted by Richelieu
OMFG! Pointers!!!! NOOOOOOOOOOOOOOOOOO!!!!

it is good to learn how to use pointers, but using malloc or new just for the hell of it is wrong.

[KrazyHorse]

Originally posted by Kuciwalker


I might as well find out how to do it now, even if it's an inefficient and more difficult way of doing things

I'm not laughing at the way you're doing it. I'm laughing at the fact that you have to do it and I don't.

God, I hated learning to program.

When my **** wouldn't compile I used to randomly insert &s and *s until it did.

[Asher]

...

One thing I have to do is randomize the contents of a matrix.

#include <stdio.h>
#include <sys/types.h>
#include <time.h>

int main()
{ 
	time_t t;
	int i, j;
	long arr[100][100];
	time(&t);
	srand48((long) t); // set seed to current time

	for(i=0; i < 100; i++) 
		for(j=0; j < 100; j++)
  			arr[i][j] = lrand48();

  return 0;
}

[Richelieu]

Originally posted by Whoha
it is good to learn how to use pointers

I did. Now I've forgotten and i don't miss them. Hated them.

[Kuciwalker]

Originally posted by Whoha
it is good to learn how to use pointers, but using malloc or new just for the hell of it is wrong.

There is no "new" in C.

@Asher: I steadfastly refuse to use the random number generator.

[KrazyHorse]

Using time seeds is frowned upon in scientific computing. There are several much more elegant solutions which have the additional benefit of being reproducible and which do not run the risk of accidental convergence between runtime of the program and the seeding.

[Asher]

Originally posted by KrazyHorse
Using time seeds is frowned upon in scientific computing. There are several much more elegant solutions which have the additional benefit of being reproducible and which do not run the risk of accidental convergence between runtime of the program and the seeding.

Are they as simple to do in stupid applications such as this?

[Kuciwalker]

Since it's prompted by user input there, it's not a problem.

[Provost Harrison]

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