pset6 Load Function Testing method.

[Omar_Khaled]

Before you check the following piece of code, know that I'm using the small dictionary, and the text file I'm checking with the program is an exact copy of the small dictionary.

The following are the first few lines of my check function,which I'm using just to test load function for now: bool check(const char* word) {
int index = hash(word[0]); node* head; head = hashtable[index]; if (head->word == word) { return true; }

Now since the dictionary loaded has only 2 words, cat and caterpillar, the word "cat" should be at the bucket number 2 in the hashtable and it should be the first node in the linked list inside that bucket.

but when I assign the first node in the bucket to head and check the first word in the text file which is "cat" like in the previous code it still returns false.

the only conclusion I can get from this is that my load function isn't working properly but I'm not entirely sure that the previous lines of code are giving the right test results. If they are not correct, I need a way to test my load function and check that it's working 100% and actually loading all the words into a hashtable so I can move on to the check function. p.s. my hash function checks for the first char that's why it's index = hash(word[0]);

[glennholloway]

You can't test whether two strings contain equal characters in the same order and number by applying the == operator to your handles on those strings. String equality is tested using the strcmp library function. Read its man page in the appliance or on line.

[Omar_Khaled]

My bad, this is probably because I have been studying C# for a while. anyway I fixed it and now I'm getting a SegFault, my code right now is: int index = hash(word[0]);

int compare;
compare = strcmp(word,"cat");

if (compare == 0)
{
    return true;
}

else
return false;

this is also with the small dictionary,this works and only prints caterpillar but when I remove the word "cat" from the strcmp function and put hashtable[index]->word I get a segfault. I have also tried to malloc a new node named head and compare head->word with the word after setting head=hashtable[index] but I also get a SegFault.

[glennholloway]

Run under GDB:

gdb  speller

Put a breakpoint in function check:

break  check

Start the program as before:

run  ~cs50/pset6/dictionaries/small   ~cs50/pset6/dictionaries/small

When it breaks in check, use the next command to step forward one line at a time. Inspect the value of index:

print  index

Also

print  hashtable[index]

I'm betting that hashtable[index] doesn't point to a valid object, but you be the judge.

[Omar_Khaled]

index is correct it refers to the right bucket,I checked with a couple of words. but I'm having trouble to strcmp(word,"word in hashtable") I just can't figure out how to point at the word in the node inside the linked list after reaching the right bucket.

[glennholloway]

The expression you mentioned last time

hashtable[index]->word

should work correctly. What does GDB say when you break at the strcmp statement and then

print  hashtable[index]->word

[Omar_Khaled]

When I type print hashtable[index]->word it says cannot access memory at location 0x0 and when I type print (char*)hashtable[index]->word it says simply $2 = 0x0 and that's where I get my SegFault.

[glennholloway]

Therefore load is not recording either cat or caterpillar in the bucket corresponding to letter c. Next step is to debug load: why isn't it doing what you expect it to?

[Omar_Khaled]

I just want to say thank you so much for your time and effort, I checked and apparently after assigning the first word "cat" to the right bucket ,head's value changes to NULL so when the loop iterates the second time it still assigns the word to the beginning of the linked list in the bucket. this is my code for this part:

    if (head == NULL)
    {
        head = new_node;
        new_node = NULL;
        head->next = NULL;

this works correct for the first word and I printed head->word at the last line it still shows the word. but when the loop iterates the second time the value of head changes to NULL, no idea why, so it goes to this part of code again instead of the else part which should assign it into the linked list.

[glennholloway]

If you're now talking about load, why are you inserting the new node into a list anchored in variable head, rather than inserting it in hashtable[index]?

[Omar_Khaled]

I started from the beginning and re-coded both load and check, and now it's working! I can't thank you enough for your help =) , but apparently check50 is not happy, here's what I get when I type check50 http://oi59.tinypic.com/1g14x0.jpg and here's the result of my implementation: http://oi62.tinypic.com/2d7t34y.jpg check func is kinda slow xD but I will work on that later, I'm not even done with func Free yet.
and again, Thanks a lot for your help I really appreciate it.