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Trie's in C

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Trie's in C

 
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  #1
Oct 26th, 2008
I have a homework assignment for a c class I am in currently, the assignment is to write a simple spell checker. I am having a bit of trouble understanding how to write a trie in c. A trie would be composed of nodes, which contain the following I believe:

1. char value (value of the node)
2. boolean isroot (is this the root node)
3. boolean endsword (is this the end of a word)
optionally
4. Node *nextnode ( a pointer to the next node if one exists).

What I am confused on, is how this should be written as an ADT in c. I have found a few samples online based in Java, but they tend to have too many features.
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Re: Trie's in C

 
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  #2
Oct 26th, 2008
I would also like to add they need a 2nd pointer to the next sibling.
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Re: Trie's in C

 
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  #3
Oct 26th, 2008
So I have been working a bit further but seem to have something wrong in my code. The header file for each node is this "node.h"
c Syntax (Toggle Plain Text) 
  1. #include <stdbool.h>
  2. #include <stdio.h>
  3. #include <stdlib.h>
  4. #include <string.h>
  5. #include <ctype.h>
  6. #include <stdbool.h>
  7.  
  8. typedef struct node { 
  9. 	char value;
  10. 	bool isroot;
  11. 	bool isend;
  12. 	struct node* sibling;
  13. 	struct node* child; 
  14. }

The code for my test of the node structure is this "node.c"
c Syntax (Toggle Plain Text) 
  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <string.h>
  4. #include <ctype.h>
  5. #include <stdbool.h>
  6. #include "node.h"
  7.  
  8. int main(void){
  9. 	return 0;
  10. }

The makefile reads as such:
C Syntax (Toggle Plain Text) 
  1. CC=gcc
  2. CFLAGS=-Wall -g
  3.  
  4. eread:	node.o
  5. 	$(CC) $(CFLAGS) -o $@ node.o
  6.  
  7. node.c: node.h

And finally the error message is this
C Syntax (Toggle Plain Text) 
  1. $ make
  2. gcc -Wall -g   -c -o node.o node.c
  3. node.c:6: error: syntax error at end of input
  4. make: *** [node.o] Error 1

Any ideas what is going on here?
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Re: Trie's in C

 
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  #4
Oct 26th, 2008
Missing ; at end of typedef.
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Re: Trie's in C

 
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  #5
Oct 26th, 2008
so new header file is this:
c Syntax (Toggle Plain Text) 
  1. #include <stdbool.h>
  2. #include <stdio.h>
  3. #include <stdlib.h>
  4. #include <string.h>
  5. #include <ctype.h>
  6. #include <stdbool.h>
  7.  
  8. typedef; struct node { 
  9. 	char value;
  10. 	bool isroot;
  11. 	bool isend;
  12. 	struct node* sibling;
  13. 	struct node* child; 
  14. }

And the error message then becomes:
C Syntax (Toggle Plain Text) 
  1. $ make
  2. gcc -Wall -g   -c -o node.o node.c
  3. In file included from node.c:6:
  4. node.h:8: warning: useless storage class specifier in empty declaration
  5. node.h:8: warning: empty declaration
  6. node.c:8: error: two or more data types in declaration specifiers
  7. node.c:8: warning: return type of ‘main’ is not ‘int’
  8. node.c: In function ‘main’:
  9. node.c:9: error: incompatible types in return
  10. node.c:10: warning: control reaches end of non-void function
  11. make: *** [node.o] Error 1

The warnings are not as troubling to me as the errors, though I am pretty sure that whatever is causing them is related.
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Re: Trie's in C

 
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  #6
Oct 26th, 2008
Funny:
c Syntax (Toggle Plain Text) 
  1. typedef struct node { 
  2. 	char value;
  3. 	bool isroot;
  4. 	bool isend;
  5. 	struct node* sibling;
  6. 	struct node* child; 
  7. }; //<== if semicolon goes here, it's much more reasonable
Last edited by Sci@phy; Oct 26th, 2008 at 7:34 pm.
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Re: Trie's in C

 
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  #7
Oct 26th, 2008 
typedef struct node { 
	char value;
	bool isroot;
	bool isend;
	struct node* sibling;
	struct node* child; 
};
He meant there.
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Re: Trie's in C

 
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  #8
Oct 26th, 2008
Wow... now I feel... dumb . Anyway brings me to a final warning
C Syntax (Toggle Plain Text) 
  1. $ make
  2. gcc -Wall -g   -c -o node.o node.c
  3. In file included from node.c:6:
  4. node.h:14: warning: useless storage class specifier in empty declaration
  5. gcc -Wall -g -o eread node.o

What exactly does this mean?
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Re: Trie's in C

 
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  #9
Oct 26th, 2008
Do you know why do you use typedef?
It's syntax should be:
c Syntax (Toggle Plain Text) 
  1. typedef some huge type A_DEF;

And the code you wrote has no use from typedef since you haven't specified name that will replace that struct.
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Re: Trie's in C

 
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  #10
Oct 26th, 2008
>What exactly does this mean?
typedef struct node { 
	char value;
	bool isroot;
	bool isend;
	struct node* sibling;
	struct node* child; 
} aliasname;
Where aliasname is any identifier you want to substitute struct node for.
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