Question about "random"

[TheDudiful]

So I have these character functions:

char a0 = '-', a1 = '-', a2 = '-', a3 = '-', a4 = '-', a5 = '-', a6 = '-', a7 = '-', a8 = '-', a9 = '-';
char b0 = '-', b1 = '-', b2 = '-', b3 = '-', b4 = '-', b5 = '-', b6 = '-', b7 = '-', b8 = '-', b9 = '-';
char c0 = '-', c1 = '-', c2 = '-', c3 = '-', c4 = '-', c5 = '-', c6 = '-', c7 = '-', c8 = '-', c9 = '-';
char d0 = '-', d1 = '-', d2 = '-', d3 = '-', d4 = '-', d5 = '-', d6 = '-', d7 = '-', d8 = '-', d9 = '-';
char e0 = '-', e1 = '-', e2 = '-', e3 = '-', e4 = '-', e5 = '-', e6 = '-', e7 = '-', e8 = '-', e9 = '-';
char f0 = '-', f1 = '-', f2 = '-', f3 = '-', f4 = '-', f5 = '-', f6 = '-', f7 = '-', f8 = '-', f9 = '-';
char g0 = '-', g1 = '-', g2 = '-', g3 = '-', g4 = '-', g5 = '-', g6 = '-', g7 = '-', g8 = '-', g9 = '-';
char h0 = '-', h1 = '-', h2 = '-', h3 = '-', h4 = '-', h5 = '-', h6 = '-', h7 = '-', h8 = '-', h9 = '-';
char i0 = '-', i1 = '-', i2 = '-', i3 = '-', i4 = '-', i5 = '-', i6 = '-', i7 = '-', i8 = '-', i9 = '-';
char j0 = '-', j1 = '-', j2 = '-', j3 = '-', j4 = '-', j5 = '-', j6 = '-', j7 = '-', j8 = '-', j9 = '-';

and I want to another function to randomly pick one of them, how can I do this?
Thanks in advance

[Athar]

char randomMinus='-';

You also need to read up on arrays before you continue.

[TheDudiful]

char randomMinus='-';

You also need to read up on arrays before you continue.

I also need this to work if they have other values than '-'

[Athar]

Yeah, you need to look up arrays and replace those one hundred variables with a single array.
Then choosing a random element will be easy.

[Stewbond]

Unfortunately, it would be VERY difficult to randomly select one of these because all of these chars are in the memory in different places.

My suggestion is to do the following instead:
char Reference[10][10] = {{'-'}};
This will create a single variable with 100 elements that can be referenced very easily. All of the elements will be initialized with a dash. To randomly select an element:

#include <stdlib.h> // Used for srand() and rand()
#include <time.h> // Used for time() which seeds the srand()

int main ()
{
  srand ( time(NULL) ); //Seed the random number generator with a different number each time.

  char Reference[10][10] = {{'-'}}; // Create the 2-d array
  int x = rand()%10; // Choose an X value between 0~9
  int y = rand()%10; // Choose a Y value between 0~9

  Reference[x][y]; //this is your random element,  write something to it, or use it at will.

  return 0;
}

If 2-d arrays aren't your thing or are unnecessary, make it a long 1-d array which would be useful if you are just learning about arrays.

#include <stdlib.h> // Used for srand() and rand()
#include <time.h> // Used for time() which seeds the srand()

int main ()
{
  srand ( time(NULL) );

  char Reference[100] = {'-'}; // Create the 1-d array
  int i = rand()%100; // Choose an i value between 0~99

  Reference[i]; //this is your random element,  write something to it, or use it at will.

  return 0;
}

[TheDudiful]

So, say I would do this:

char array[9][9] {	{-,-,-,-,-,-,-,-,-,-},
			{-,-,-,-,-,-,-,-,-,-},
			{-,-,-,-,-,-,-,-,-,-},
			{-,-,-,-,-,-,-,-,-,-},
			{-,-,-,-,-,-,-,-,-,-},
			{-,-,-,-,-,-,-,-,-,-},
			{-,-,-,-,-,-,-,-,-,-},
			{-,-,-,-,-,-,-,-,-,-},
			{-,-,-,-,-,-,-,-,-,-},
			{-,-,-,-,-,-,-,-,-,-}};

I could access what in my first post would be a0 with:
array[0][0]

And isn't there a way to get the desired result without the array?

EDIT: Thanks Stewbond, I'll try that if it is that much easier than when I use a single variable for every one of them

[Stewbond]

If you already have a program written which uses all of those individual chars, then it IS possible to access them by random, but you still need to create an array like the one I created above. I'm still not great with pointers, but I think the following would work:

#include <stdlib.h> // Used for srand() and rand()
#include <time.h> // Used for time() which seeds the srand()
...
srand ( time(NULL) );

//This sets each element of the array to the ADDRESS of each label you made
char Reference[100] = {&a0 ,&a1,...,&j8,&j9}; // Create the 1-d array (replace ... with the other 96 variables)
int i = rand()%100; // Choose an i value between 0~99

//This returns the VALUE at each address.
*Reference[i]; //this is your random element,  write something to it, or use it at will. 

[TheDudiful]

When I use srand ( time(NULL) );
I get the error message:

expected `,' or `;' before '(' token

EDIT: And

expected constructor, destructor, or type conversion before '(' token 

[Stewbond]

For your error message, look at what is ahead of srand. It means that you probably haven't entered a condition after an if statement or while loop or something. Also check that all of the {s have matching }s ahead of srand.

Note, srand only needs to be set once in a program. It is probably best to do it at the start of your main instead of in a loop to ensure that you don't get some non-random behavior.

Oh, and in response to your post above (that I didn't see), here are a few tips:
1. array[9][9] has a 9X9 grid (81 elements) and you can only access elements 0-8 (9 elements total) in each axis. You should make it array[10][10] to ensure you have a 10x10 grid (100 elements) and you can access elements 0-9 (10 entries) in each axis.
2. array[10][10] = {{'-'}}; is a shorthand way of filling all elements with the dash character, you don't have to type it manually like you did.