comparison is always true/false

jubaitca · 11-03-2006, 03:51 PM

I am getting an error when i try to compare a character to check if has the escape character. But this give me the following error when i run it:

inputfile.c:29:28: warning: unknown escape sequence '\o'
inputfile.c:33:33: warning: unknown escape sequence '\o'

My code is the following:

int main(int argc, char *argv)
{
int const MAX_WORDS = 10000;
int const MAX_WORD_LENGTH = 25;
char words [MAX_WORDS][MAX_WORD_LENGTH+1];
ifstream inputFile;
inputFile.open("WarOfTheWorlds-Ch1.txt");
char a;
int number_words = 0;
for (int i = 0; (i <= 10000) && (!inputFile.eof()) ; i++)
{
bool check_space =true;
for (int j = 0;((j <= 25) && (! inputFile.eof()) && (check_space)); j++)
{

inputFile.get(a);
if ((a != ' ') && (a != '\o'))
{
words [i][j] = tolower(a);
}
else if ((a == ' ') || (a == '\o'))
{
check_space = false;
}
}
number_words++;
}
cout << words[5];
}

tuxdev · 11-03-2006, 03:59 PM

Erm, '\o' isn't a valid C escape code, just like the compiler told you. Perhaps you mean '\0'? Also, please wrap code in [code] tags for readiblity.

demon_vox · 11-03-2006, 04:21 PM

Yes tuxdev is right. The end of an array of characters is a '\0' (and that is a zero, just in case).
But I also see that you are using C++ objets and your file's name ends up with .c. Maybe you should be consistent and work in one language or the other. Plus I believe that if you are coding in C++ you have a string class which is much happier

(yet its been a while since I wrote a line of C++ so I cant point much more information on this topic).

Cheers!

jubaitca · 11-03-2006, 04:32 PM

Quote:

Originally Posted by tuxdev

Erm, '\o' isn't a valid C escape code, just like the compiler told you. Perhaps you mean '\0'? Also, please wrap code in [code] tags for readiblity.

but is the '\0' a escape character, so that when i check it it means that it is the end of the word? The purpose of my program is to store all the words in the array words[][]. But what happens is that when there is a newline, it takes in two words instead of one.

And also, I am supposed to do this in C++, that's how i was taught to do c++, so this code is intended to be C++.

thanks

jubaitca · 11-03-2006, 05:10 PM

i fixed the problem - instead of using the get function, i used the extraction operator. My next problem is that i have to remove all the punctuation marks at the begenning or end of the word, but not in the middle. How should i do this?

Thanks

jubaitca · 11-04-2006, 10:12 AM

ok....say I am using two char arrays (2 dimensional) how can i store everything from one array to the other except the first index? because strncpy starts from the first index right?

jubaitca · 11-04-2006, 10:30 AM

well this what tried until now to remove the punctuations is its in the first index

Code:

                         else if ((!(isalpha(words[i][0]))) ||
			(!(isdigit(words[i][0]))))
			{
			new_words[i][j] = words[i][j+1];
			}

Although this compiles, its not actually working for me.

dogpatch · 11-04-2006, 05:59 PM

Code:

 
else if ((!(isalpha(words[i][0]))) ||
                        (!(isdigit(words[i][0]))))

will always be true

Try this instead to test for alpha or numeric character:

Code:

else if (!isalnum(words[i][0]))

jubaitca · 11-04-2006, 06:14 PM

oh ok thanks. Actually the compiler was right.

But now I have to sort the words. The following is my sorting code, but it gives me a lot of errors for some reason.

If someone could just tell me a general problem for the code, I would really appreciate it. Thanks in advance

Code:

Code:

void SelectionSort(int arr[][MAX_WORD_LENGTH+1], const int size)
{
	int smallest_index;

	for (int i= 0; i <=size; i++)
	{
		smallest_index = i;
		
		for (int j = i + 1; j <= size; j++)
		{
			if (strcmp(arr[j],arr[smallest_index]) < 0)
			{
			 	smallest_index=j;
			}
		
		}
		swap(arr[i],arr[smallest_index]);
	}			
}

void swap_words(char arr[],char arr2[])
{
	char temp[strlen(arr1)];
	strncpy(temp,arr1,strlen(arr1));
	strncpy(arr1,arr2,strlen(arr2));
	strncpy(arr2,temp,strlen(temp));
}

Errors:
test.c: In function `void SelectionSort(int (*)[26], int)':
test.c:67: error: cannot convert `int*' to `const char*' for argument `1' to `in
t strcmp(const char*, const char*)'
test.c: In function `void swap_words(char*, char*)':
test.c:79: error: `arr1' undeclared (first use this function)
test.c:79: error: (Each undeclared identifier is reported only once for each fun
ction it appears in.)
test.c:80: error: `temp' undeclared (first use this function)
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_algobase.h: In function `
void std::swap(_Tp&, _Tp&) [with _Tp = int[26]]':
test.c:73: instantiated from here
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_algobase.h:130: error: in
valid initializer
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_algobase.h:131: error: IS
O C++ forbids assignment of arrays
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_algobase.h:132: error: IS
O C++ forbids assignment of arrays

tuxdev · 11-04-2006, 06:34 PM

This code is so wrong in so many ways. When you pass arrays around, you must pass their sizes too. Don't use int if you mean char, as in null terminated strings. You 've got a type in the prototype of swap_words. And most of all, you really should be using std::string and std::vector.

jubaitca · 11-04-2006, 07:08 PM

well im not allowed to use vectors yet. I don't understand, how I would pass the sizes, if the size depends on what is being passed. Can you please give an example of where this can be fixed? And also can you tell me which int are you refferring to that is supposed to be char?

Thanks

tuxdev · 11-04-2006, 07:58 PM

Quote:

test.c:67: error: cannot convert `int*' to `const char*' for argument `1' to `in
t strcmp(const char*, const char*)'

This is the compiler telling you that you are trying to put an int* where a const char * should be.

Quote:

test.c:79: error: `arr1' undeclared (first use this function)

This is the compiler telling you that you are trying to use something you haven't told exists (due to a typo).

Your array really should be an array of pointers with dynamically allocated stuff, then just swap pointers, not pointer contents. Copying is slow.

jubaitca · 11-04-2006, 09:00 PM

ok, to tell you the truth, I am really a newbie at C++. I am just learning it at the moment. I haven't learned pointers yet. My teacher said to sort all the words in alphabetical order. My algorithm to do this is to check all the words (which are stored in the array) with the cstring function cstrncmp and then sort it accordingly. To sort it I use the swap function.

tuxdev · 11-04-2006, 09:06 PM

Ouch, Ouch Ouch. Do you have a copy of K&R C? It might be really useful reading for you.

Other than the implementation is really bad (sorry it is forced onto you), and definitely the hard way, I don't see any glaringly obvious bugs other than what the compiler told you.

jubaitca · 11-04-2006, 09:19 PM

well, my teacher said I can't use anything that hasn't been taught in class yet. So I am stuck with everything up to cstring. That's about all. I was wondering if you can please give me a hand with my algorithm (my basic approach to do it). Is there something wrong with it?

By the way I am currently studying from the textbook "Problem Solving with C++" by walter savitch.