how to read a txt file into an array

[nar0122]

I have a text file called A.txt that I am trying to read each character frequency from. The best way to show my problem is by example. Say the file reads "AbCAAb",

I have created an array of 256 memory positions to store each character frequency. So, first we encounter a capital A, which is the ascii value 65. So I go to position 65 in the array, and increment the count to 1. Then little b is 97, so I go to position 97 in the array...once I hit the next capital A, it should go to position 65 in the array and increment its counter to 2, then 3 for the next A. In the end, I should have an array consisting of zeros, where there were some characters that were not found in the file, and the frequencies of characters in the file that were found.

*************** *************** *************** *************** **********
THIS IS MY CODE THUS FAR
*************** *************** *************** *************** **********
//ignore the test points, they are for debugging purposes

int getFrequency(int arrayOfCharacters[])
{
	ifstream in;
	in.open("A.txt");
	cout<<"TEST POINT 2\n";
	for(int i = 0; i < 256; i++)
	{
		arrayOfCharacters[i] = 0;
	}

	cout<<"TEST POINT 3\n";
	int c = in.get();
	arrayOfCharacters[c]++;

	
	while(c!=EOF)
	{
	c = in.get();
	arrayOfCharacters[c]++;
	
	}

	for(int j = 0; j < 256; j++)
	{
		cout<<arrayOfCharacters[c];
	}

	in.close();
	return c;
	
}

[weaknessforcats]

Remember that arrays are 0 based. The 65th element for your A is array[64].

[whodgson]

So what succes have you had to date? What is your question?
Woops how do you read a text file into an array?....right ?
Use the cin.getline () function after opening the file in read mode (r).

[nar0122]

So far I am getting the right results in the array aside from the last character in the array. Everything looks to be right, then I am getting a large number like 4677907 in the very last position in the array? I also need to know how to make the out put say, "There are (number of characters) (character)."

Example: File has "AAAaaa"

Output should read:

There are 3 A's.
There are 3 a's.

[weaknessforcats]

Are you using array[256] as your last element?

If you are, you need a 257 element array.

That would explain the garbage in the last element. Apparently my Post #2 wasn't clear enough.

[jfwfmt]

You are probably not checking for end of file correctly. Look at the documentation of .get() and its friends (google get())

/s/ Jim WIlliams

also note that 0-037, 0177 and 0200-0237 (octal) are not directly printable

[donbock]

Don't know about C++, but in C the char type can be either signed or unsigned. To be fully portable you should do something to insure that you never use a negative array index.

[donbock]

The following snippets show how to maximize portability by rooting out assumptions about implementation-dependent behavior.

#include <limits.h>        // Obtain UCHAR_MAX.
#define NCHARACTERS (UCHAR_MAX + 1)    // Don't assume 256.
...
int countingArray[NCHARACTERS];
...
int i, c;
...
for (i=0; i<NCHARACTERS; i++) {
    countingArray[i] = 0;
}
...
do {
    c = in.get();
    if (c != EOF)
    {
        i = ((unsigned char) c);    // Protect from compilers where char is signed.
        countingArray[i]++;
    }
} while (c != EOF);
...
for (i=0; i<NCHARACTERS; i++) {
    c = ((char) ((unsigned char) i));        // Recover printable character code (if you need it).
    ...
}

I'm not sure the casts on lines 16 and 22 are fully portable, but it seems reasonable to expect char and unsigned char to be interconvertibl e regardless of the integer encoding used by the compiler.

The double-cast on line 22 is probably excessive. On most (perhaps all) platforms it would be ok to cast directly from int to char.

[weaknessforcats]

I am going to offend someone, I just know it, but here goes:

1) The C++ header is <limits> and not <limits.h>. None of the standard C++ headers is guaranteed to be C-compatible and <limits> is a good example. All .h standard header are fo C. C++ standard headers have no extension and are in the std namespace.

2) In C++ you use the numeric_limits template for info on your type rather than the C sizeof.

3) There is no C cast in C++. The cast form (char) is compilable in C++ only as a backwards compatible feature. It doesn't work the same in C++ as in C. Using this in C++ will call conversion operator, if available. You are supposed to use the C++ cast forms.

4) The only time you need to cast in C++ is a) you are calling a relic C function that has a void* argument or some such or b) your C++ design is screwed up.

5) Prefer using vector to using arrays.

6) Prefer using the accumulates algorithm to writing loops.

7) Do not use macros in C++. There are several features in C++ that are direct maco replacements: a) templates, b) inline functions, c) enums, d) namespaces.