Thread: Function problems

Originally Posted by matsp

In some respects, I think the same about (void) in function the function argument list in C++.

There's something I just have to hate. Void does not need to be used in argument lists in C++. It just tends to look ugly. Knowing that I have to use "..." to create variables argument lists, I really think void can be left out.

So how would that work in a 5X5 or 6X5 grid? Surely there is a minimum grid and even perhaps a maximum grid.

A grid of 1 or 2 is impossible. A grid of 3 is only good for a single character, so also no good.

It's not until you get a grid of 7X7 that a 5X5 digit will fit, which is probably the first one where all digits could be recognized, and that's with no space between it and the grid.

... thinking... drawing....

Hold the phone - I've figured this out.

If you map a 5X5 character, you can then apply enough rules to scale them all. Look at this picture of 3. The (complicated) rules would apply to all numbers. Basically, it works with the concept of filler positions. Row1, 3 and 5 need to be respected, and col1, col3 and col5 need to be respected. Everything else can be repeated. It should work for all digits. You get to define them and structure the program to do the rest.

And, the code to get you started... (you're welcome)

Code:

#include <stdio.h> 

void print_digit(char c[5][5], int newgrid_dim ) ; 

int main(void) { 

char grid3[5][5] = {   // the character "3" 
	{ '*','*', '*','*', '*' } , 

	{ ' ',' ', ' ',' ', '*' } , 

	{ '*','*', '*','*', '*' } , 

	{ ' ',' ', ' ',' ', '*' } , 

	{ '*','*', '*','*', '*' } }  ; 
	
	int newgrid_dim = 9 ; 

	int newgrid_center = (newgrid_dim+1) / 2 ; 

	int i , j ;  // dimension of new grid (row, col) 
	int a , b ;  // dimension of grid3 

//	char * gridptr ; 
//	gridptr = grid3 ; 

	print_digit(grid3, 9) ; 
}

void print_digit(char grid[5][5] , int newgrid_dim) {  

	int newgrid_center = (newgrid_dim+1) / 2 ; 

	int i , j ;  // dimension of new grid (row, col) 
	int a , b ;  // dimension of grid3 

	for (i = 1 ; i <= newgrid_dim ; ++i ) { 
		for (j = 1 ; j <= newgrid_dim ; ++j ) { 
			if (i==1) a = 1 ; 
			else if (i < newgrid_center) a = 2 ;   // filler position
			else if (i == newgrid_center) a = 3 ; 
			else if (i < newgrid_dim) a = 4 ;  // filler position 
			else a = 5 ; 	

			if (j==1) b = 1 ; 
			else if (j < newgrid_center) b = 2 ;   // filler position
			else if (j == newgrid_center) b = 3 ; 
			else if (j < newgrid_dim) b = 4 ;  // filler position 
			else b = 5 ; 

			// a & b are now set to point to the proper character to write 
			// at i,j 
			printf("%c", grid[a-1][b-1] ) ; 
		}
		printf("\n") ; 
	} 
}

Code:

#include <stdio.h> 

void print_digit(char c[5][5], int newgrid_dim ) ; 

int main(void) { 
	char grid3[5][5] = {   // the character "3" 
		{ '*','*', '*','*', '*' } , 

		{ ' ',' ', ' ',' ', '*' } , 

		{ '*','*', '*','*', '*' } , 

		{ ' ',' ', ' ',' ', '*' } , 

		{ '*','*', '*','*', '*' } }  ; 
	
	int newgrid_dim = 9 ; 

	int newgrid_center = (newgrid_dim+1) / 2 ; 

	int i , j ;  // dimension of new grid (row, col) 
	int a , b ;  // dimension of grid3 

//	char * gridptr ; 
//	gridptr = grid3 ; 

	print_digit(grid3, 9) ; 
}

void print_digit(char grid[5][5] , int newgrid_dim) {  

	int newgrid_center = (newgrid_dim+1) / 2 ; 

	int i , j ;  // dimension of new grid (row, col) 
	int a , b ;  // dimension of grid3 

	for (i = 1 ; i <= newgrid_dim ; ++i ) { 
		for (j = 1 ; j <= newgrid_dim ; ++j ) { 
			if (i==1) a = 1 ; 
			else if (i < newgrid_center) a = 2 ;   // filler position
			else if (i == newgrid_center) a = 3 ; 
			else if (i < newgrid_dim) a = 4 ;  // filler position 
			else a = 5 ; 	

			if (j==1) b = 1 ; 
			else if (j < newgrid_center) b = 2 ;   // filler position
			else if (j == newgrid_center) b = 3 ; 
			else if (j < newgrid_dim) b = 4 ;  // filler position 
			else b = 5 ; 

			// a & b are now set to point to the proper character to write 
			// at i,j 
			printf("%c", grid[a-1][b-1] ) ; 
		}
		printf("\n") ; 
	} 
}

You should know that everything inside a function should be indented. It makes it confusing otherwise...

Yes, I missed that one. No comments about the cleverness of the algorithm??

I'm not one for algorithms
Difficult to understand most of the times...

No void in C meant variable arguments. Void in C++ is not necessary, but may be added to explicitly declare there should be no variable argument list, in response to mats's reply.

Originally Posted by Elysia

No void in C meant variable arguments. Void in C++ is not necessary, but may be added to explicitly declare there should be no variable argument list, in response to mats's reply.

empty parameter list in C means variable arguments.
That's why void as a parameter list in C is required to specify the function with no arguments.

empty parameter list in C++ means no arguments, that's why void in parameters list is fully equivalent to empty parameters list and could be fully avoided in C++.

It is used only to make code in headers look like the C-code

OP:

Originally Posted by Elysia

No void in C meant variable arguments. Void in C++ is not necessary, but may be added to explicitly declare there should be no variable argument list, in response to mats's reply.

There is a world of difference in what she's saying and what is true. Actually, in C, empty parens is an undefined argument list in the sense that you can pass anything and the compiler ignores that. Variable argument lists can be passed "anything" too, but the arguments during he call are contained in a va_list. The prototypes for these functions is obvious. That allows you to take some advantage of the arguments you pass. Using an undefined argument list you can't make an assumption what arguments are named or their types, and there is nothing like va_list to maintain them.

In C++, empty parens is an empty argument list, but only because Stroustrup designed things this way. Ugly or not, void will still be necessary in code that "crosses the aisle" to C.

Originally Posted by citizen

In C++, empty parens is an empty argument list, but only because Stroustrup designed things this way. Ugly or not, void will still be necessary in code that "crosses the aisle" to C.

C++ is not C.
Void is not necessary in argument list so long as you don't compile it as C.
Which is my point. It's ugly and undeserving.