So I've been taking Harvard's CS50 class and currently am working on it's Problem Set 5 called speller ( https://cs50.harvard.edu/x/2020/psets/5/speller/ )
Basically I think that I have filled everything correctly, however, when trying to compile this error message appears :
In function `check':/home/ubuntu/pset5/speller/dictionary.c:33: undefined reference to `hash' dictionary.o: In function `load': /home/ubuntu/pset5/speller/dictionary.c:90: undefined reference to `hash' clang-7: error: linker command failed with exit code 1 (use -v to see invocation)
I am not sure what this means, and tried to figure it out for quite some time, but I'm reaching out for an explanation...
My code is :
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <ctype.h>
#include "dictionary.h"
int word_count = 0;
// Represents a node in a hash table
typedef struct node
{
char word[LENGTH + 1];
struct node *next;
}
node;
// Number of buckets in hash table
const unsigned int N = 26;
// Hash table
node *table[N];
// Returns true if word is in dictionary else false
bool check(const char *word)
{
unsigned int h = hash(word);
node *cursor = table[h];
while(cursor != NULL)
{
if(strcasecmp(word, cursor -> word) ==0)
{
return true;
}
else
{
cursor = cursor -> next;
}
}
return false;
}
// Hashes word to a number
// This hash function was adapted by Neel Mehta from
// http://stackoverflow.com/questions/2571683/djb2-hash-function.
unsigned int hash_word(const char* word)
{
unsigned long hash = 5381;
for (const char* ptr = word; *ptr != '\0'; ptr++)
{
hash = ((hash << 5) + hash) + tolower(*ptr);
}
return hash %26;
}
// Loads dictionary into memory, returning true if successful else false
bool load(const char *dictionary)
{
FILE *dic = fopen(dictionary, "r");
char word[LENGTH + 1];
if(dic == NULL)
{
unload();
return false;
}
while (fscanf(dic,"%s",word) != EOF)
{
node *sllnode = malloc(sizeof(node));
if( sllnode == NULL)
{
return false;
}
strcpy(sllnode -> word, word);
word_count++;
int dicindex = hash(word);
if(table[dicindex] == NULL)
{
sllnode -> next = NULL;
}
else
{
sllnode -> next = table[dicindex];
}
table[dicindex]= sllnode;
}
fclose(dic);
// check here whethet to free memory space or not (maybe needs to be freed at very end)
return true;
}
// Returns number of words in dictionary if loaded else 0 if not yet loaded
unsigned int size(void)
{
return word_count;
return 0;
}
// Unloads dictionary from memory, returning true if successful else false
bool unload(void)
{
for(int i = 0; i < N ; i++)
{
node *cursor = table[i];
while(cursor)
{
node *tmp = cursor;
cursor = cursor -> next;
free(tmp);
}
}
return true;
}
If you would like to know what dictionary.h looks like, here is the code for that:
// Declares a dictionary's functionality
#ifndef DICTIONARY_H
#define DICTIONARY_H
#include <stdbool.h>
// Maximum length for a word
// (e.g., pneumonoultramicroscopicsilicovolcanoconiosis)
#define LENGTH 45
// Prototypes
bool check(const char *word);
unsigned int hash(const char *word);
bool load(const char *dictionary);
unsigned int size(void);
bool unload(void);
#endif // DICTIONARY_H
Hoping someone could help me with this.. Any help would be appreciated!
If you look in your load()
function, you have this line: int dicindex = hash(word);
.
The issue with this is that you changed hash()
into hash_word()
which is why you are having the error because there is no hash()
function in the code. Easiest thing to do is to change unsigned int hash_word(const char* word)
back to normal which was unsigned int hash(const char* word)
as you weren't suppose to change any function name in this program.
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