Help for another program

[Androto]

void count_chars()
{
for(unsigned i=0; i<sSentence.size(); ++i)
for(unsigned j=0; j<CHARS; ++j)
if( sSentence.substr(i,1) == theAlphabet.substr(j,1) )
theAlphabetCount[j]++;
}

this is the last thing i don't get

[Valmont]

First of all I updated the code. Use the new version.

- The CTRL-Z thing:
Terminating immediatly after CTRL-Z is not an option with me since I support only STANDARD C++ as defined by ISO C++. I'll explain:
If it would terminate immediatly I would need operating specific methods. But standard C++ doesn't know about operating systems. So I don't know about them either.
What happens now, is that something needs to be stored in sSentence. But if CTRL-Z is ENTERED, it is assumed that end-of-file is reached. We trap EOF by using cin.eof and leave that function.

- unsigned theAlphabetIndex[52]={0};
1)I didn't define this before. Read carefully how they are named.
Also I renamed this array because it isn't indexing (well that too as it happens) but its main purpose is to keep track of used character (how often they are used).
2) the "={0}" part means that I am assigning this array with zero's.
I do that because all characters are used 0 times when the application starts.
3) Index 0 refers to letter a, while index 51 refers to the letter Z (capital). That's how it works.

- while( !(getline(cin, sSentence)) || sSentence.size()==0 )
This is a neat one huh?
1) getline() fetches the complete stream, including leading spaces, tabs,etc.
2)but while(!(getline(cin, sSentence) ) means:
"As long as sSentence didn't receive anything VALID..."
3)and while( !(getline(cin, sSentence)) || sSentence.size()==0 )
means:
"As long as sSentence didn't receive anything VALID or sSentence didn't receive anything AT ALL..."

So sSentence needs to get something, and it must be something valid too!
However, EOF is valid as well. So the cin.eof checks if we actually did enter CTRL-Z/D. If so, then we leave the functions instead of asking for input again.

Since sSentence is a std::string, this variable can hold almost anything, if the right functions are used. So IF
!(getline(cin, sSentence))
occurs, something must be terribly wrong! But the chances are slim for that to happen. Nevertheless, we code neat.

[Androto]

thx for the explanation and the program. i'm going to add in my own comments to try to better understand the program and how it works. but i get the general idea as to how you used functions.

[Valmont]

Originally posted by Androto

void count_chars()
{
   for(unsigned i=0; i<sSentence.size(); ++i)
      for(unsigned j=0; j<CHARS; ++j)
         if( sSentence.substr(i,1) == theAlphabet.substr(j,1) )
            theAlphabetCount[j]++;
}

this is the last thing i don't get

Well this is the smart part basically. A loop in a loop.

Suppose you entered: Hi
Then this happens: sSentence.size() = 2
1) "H" is compared with all characters in the theAlphabet array.
theAlphabet array has 52 different characters in it, so "H" is compared with each of them. "H" is compared 52 times, for each character once.
2)"i" is compared with all characters in the theAlphabet array.
theAlphabet array has 52 different characters in it, so "H" is compared with each of them. "H" is compared 52 times, for each character once.

3) IF one if the characters in the sentence mathces a character in theAlphabet array, that index in theAlphabet array is raised with one.

4)sSentence.substr(i,1)
We need only ONE character of the sentence so we use std::subtr();
std::substr() extracts a part of a string in a std::string!
The first parameter is the starting-index of the string (a std::string is an array too, but a luxury one) and the second parameter is how many characters we want to extract.

Examples:
string result;
string mystring = "Hello everybody";
result=mystring.substr(3,1); // result = "l"
result=mystring.substr(3,3); //result = "lo "
result=mystring.substr(0,3); //result = "Hel"
result=mystring.substr(6,4); //result = "ever"

[Androto]

i forgot about that part, good thing you didn't.

[Valmont]

To gamehead200

Originally posted by gamehead200
Because I'm nice and its due tomorrow, here's part of my code:

while( i < sent.size() )
    {
        switch( sent[ i ] )
        {
            case 'a':
            acount++;
            break;
        }    
         
        i++;
    }

And to only show the letters that actually appear more than 0 times:

   if( acount )
        cout << "a = " << acount << endl;

Hey gamehead, it's a good start.
However, you need a long switch statement and lots of variables. Here is a global solution if you like to move on with coding:
1)Try to decouple things.
Basically ask yourself: What if I change one critical thing, how bad do other parts will perform because they depend on it? Can I make it so other parts don't (or almost don't) depend on it?

2)Make sure you know what you want:
Ask yourself: This is how my function look. But is this function really responsible for so many things?
Look at my code and observe void count_chars().
It does strictly the calculating. Nothing else at all.
While the menu-function is strictly responsible for setting up a menu and processing and validating input.
Actually, the latter is too much already!!! But you're not ready for that yet. Just a heads up though.
And finally the print function. It has some "smartness" in it, the code is so small, I made it part of the function. But I'm moving on the edge already.

Let these two things be your guide next time.

[Androto]

what does this mean:

      //Just in case.
      cin.clear();

[redhead]

make sure there arent any garbadge in the instream, incase you wanted to get something from it.

[gamehead200]

The reason why we have to use the case statements is because our teacher wants us too! By the way, Andrew, if you hand it in like that, he'll probably take off a WHOLE bunch of marks for not use the case statements...

Valmont, I highly appreciate your help... I hope to use this in the future!

[Valmont]

I had a discussion with collegues some time ago. C++ coders would be better off if half of the schools, universities and institutions stop teaching C++.
What in the name of the world do they think they achieve when practically forcing students to code 26 case statements in a switch?
No wonder that in the beginning Java was so easely sold to employers of sloppy C++ programmers. I think I finally start to see how that was possible.