Simple Structure program

This is a discussion on Simple Structure program within the C Programming forums, part of the General Programming Boards category; I wrote this very simple program to make sure I understood arrays of structures and file i/o. When I comple, ...

  1. #1
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    Simple Structure program

    I wrote this very simple program to make sure I understood arrays of structures and file i/o. When I comple, I get an error on line 28 that states 'passing arg 2 to function strcpy create pointer without cast). I has gotten this error in a simpler version (sans structures) and was rid of it by declaring the function as:
    Code:
    char blah[5];
    Now, however, the same fix isn't working. Any insight would be appreciated. The program is meant to read in a text file of 5 rows, each with 5 symbols. It creates a structure with their symbol and location, and then spits it back out.

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    
    typedef struct wildroom{
    	int x;
    	int y;
    	char symbol[1];
    } wr;
    
    int main(){
    	FILE *minimap;
    	wr wilddata[24];
    	int x,y;
    	
    	minimap = fopen("./minimap.txt","r");
    	
    	if(minimap==NULL)
    	{
    		printf("Error in File Read\n");
    		exit(0);
    	}
    	
    	for(x=0;x<5;x++){
    		for(y=0;y<5;y++){
    			wilddata[(x*5)+y].x=x;
    			wilddata[(x*5)+y].y=y;
    			strcpy(wilddata[(x*5)+y].symbol,fgetc(minimap));
    		}
    	}
    	
    	for(x=0;x<5;x++){
    		for(y=0;y<5;y++){
    			printf("%s",wilddata[(x*5)+y].symbol);
    		}
    		printf("\n");
    	}
    			
    	fclose(minimap);
    	
    	return(1);
    }

  2. #2
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    wilddata can only access wilddata[0] to wilddata[23]

  3. #3
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    Increasing the declaration to
    Code:
    wr wildata[25];
    It should take care of that, but it won't take care of the earlier warning, will it?

  4. #4
    C++まいる!Cをこわせ! Elysia's Avatar
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    Quote Originally Posted by dopejack View Post
    Code:
    	for(x=0;x<5;x++){
    		for(y=0;y<5;y++){
    			wilddata[(x*5)+y].x=x;
    			wilddata[(x*5)+y].y=y;
    			strcpy(wilddata[(x*5)+y].symbol,fgetc(minimap));
    		}
    	}
    	
    	for(x=0;x<5;x++){
    		for(y=0;y<5;y++){
    			printf("%s",wilddata[(x*5)+y].symbol);
    		}
    		printf("\n");
    	}
    Suggest you don't do things like that because it's confusing and prone to bugs and errors. Use two-dimensional arrays instead.
    And remember that if you define something as wr wildata[24], you get 24 elements, ranging from 0 to 23, and not 1 to 24.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

  5. #5
    CSharpener vart's Avatar
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    and why to encript your code?

    Code:
    wr wilddata[5][5];
    
    wilddata[x][y].symbol
    is a lot more simplier to read
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

  6. #6

  7. #7
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    Thanks for the help. I think I'm mopving in the right direction, since for the first time, I'm actually spitting back a 5x5 block of text. The code has changed to this:

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    
    typedef struct wildroom{
    	int x;
    	int y;
    	char symbol[1];
    } wr;
    
    int main(){
    	FILE *minimap;
    	wr wilddata[5][5];
    	int x,y;
    	
    	minimap = fopen("./minimap.txt","r");
    	
    	if(minimap==NULL)
    	{
    		printf("Error in File Read\n");
    		exit(0);
    	}
    	
    	for(x=0;x<5;x++){
    		for(y=0;y<5;y++){
    			wilddata[x][y].x=x;
    			wilddata[x][y].y=y;
    			fgets(wilddata[x][y].symbol, 1, minimap);
    		}
    	}
    	
    	for(x=0;x<5;x++){
    		for(y=0;y<5;y++){
    			printf("%s",wilddata[x][y].symbol);
    		}
    		printf("\n");
    	}
    			
    	fclose(minimap);
    	
    	return(1);
    }
    However, it returns 5 lines of 5 garbage characters each.
    Code:
    ^"%,
    ÄDÜčō
    
    etc...
    Thanks for the point to tutorials that actually made sense.

  8. #8
    Deathray Engineer MacGyver's Avatar
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    Use fgetc() to read a char. Using fgets() to read a char is going to screw you up. Also, don't declare a char array with a size of one. That doesn't allow you space for a '\0', and it's just asking for trouble.

  9. #9
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    Changing lines 8 and 28 to:
    Code:
    char symbol[2];
    and
    Code:
    wilddata[x][y].symbol=fgetc(minimap);
    respectively, garners me an error:
    Code:
    struct.c: 28: error: incompatible types in assignment
    *boggle* What am I missing here? Why do I have trouble assigning one variable of type char to another?

  10. #10
    Deathray Engineer MacGyver's Avatar
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    Because symbol is an array. You're trying to assign a char to a char array.

    If symbol was a char, it would work.

    If you want to keep it as an array, then you would either read the char into symbol[0], or more appropriately, you would use fgets().

    TBH, I think you should change symbol to a char (instead of a char array), unless you really need it to be an array.

  11. #11
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    Once again, another step in the right direction and my thanks. Line 8 became
    Code:
    char symbol;
    and now my map returned:

    Code:
    01234
    56789
    abcde
    fghi
    I upped the size of wilddatato
    Code:
    wilddata[6][6]
    and increased each of my loops accordingly. That netted:

    Code:
    01234
    56789
    abcde
    fghij
    klmno˙˙˙
    For clarification, the minimap file looks like this:
    Code:
    01234
    56789
    abcde
    fghij
    klmno
    Anyone on why I appear to get 19 chars back the first time and
    28 back later? Are the ends of the lines being counted as unseen characters?

  12. #12
    Deathray Engineer MacGyver's Avatar
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    I'm rather surprised that even works as well as it does, to be honest.

    Code:
    printf("&#37;s",wilddata[x][y].symbol);
    This should be with a %c.

  13. #13
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    My mistake. It already is %c. Been changed previously. Any other guesses?

  14. #14
    Deathray Engineer MacGyver's Avatar
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    Well, with your changes it works for me, except it prints an extra '\n' for each line, which you are correct, is from the file.

    This is what I tested:

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    
    typedef struct wildroom{
    	int x;
    	int y;
    	char symbol;
    } wr;
    
    int main(){
    	FILE *minimap;
    	wr wilddata[6][6];
    	int x,y;
    	
    	minimap = fopen("./minimap.txt","r");
    	
    	if(minimap==NULL)
    	{
    		printf("Error in File Read\n");
    		exit(0);
    	}
    	
    	for(x=0;x<6;x++){
    		for(y=0;y<6;y++){
    			wilddata[x][y].x=x;
    			wilddata[x][y].y=y;
    			wilddata[x][y].symbol = fgetc(minimap);
    		}
    	}
    	
    	for(x=0;x<6;x++){
    		for(y=0;y<6;y++){
    			printf("&#37;c",wilddata[x][y].symbol);
    		}
    		/*printf("\n");
    		*/
    	}
    			
    	fclose(minimap);
    	
    	return(1);
    }
    This is the file I used:

    Code:
    01234
    56789
    abcde
    fghij
    klmno

  15. #15
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    I'm using cygwin, so who knows. I've seen it be buggy before. Thanks. Tremendous confidence boost that it's at least working for SOMEONE.

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