Next character in a string?

**Bnorman** · 09-17-2009

New to C ++ programming have a course in it this semester... I am curious and I don't see it in my text, if there is a way to read the next character in a string?

Suppose the user enters a string of "tree" I need to capture each letter individually and then pass that value off to another part of the program.

The problem I am working on is to take an user input string and then have it spelled out military style

So if the user input the word "tree" I need to come back with tango romeo echo echo as my output... and I am trying to do that by breaking the string into single characters and passing their value to a switch, but as my post indicates I'm stuck! LOL

Any help is greatly appreciated!

**gamer4life687** · 09-17-2009

Loop through the string and use either .at() or [] to access the specific characters.

**Bnorman** · 09-17-2009

Is that to say find the length () and then just use a loop to increment until the end of the string is reached? Again I'm a beginner so I am having to look through my text book for something I think could do that... I'm currently on the idea of using a loop to increment a substr function...
for "tree" length would be 4 so I'm thinking mystring.substr (0,1) loop and then do mystring.substr(1,1) am I on the right track there?

**gamer4life687** · 09-17-2009

Look at the std::references. string - C++ Reference

length() is provided for you. There isn't much work for you to do.

**gamer4life687** · 09-17-2009

Do you need to store the individual letters or just output their translation?
If just output it's straightforward.

Code:

string text = "tree"; //get it from user doesn't matter.

for(int i = 0; i < text.length(); i++){
         switch(text[i]) { 
                case 'a': 
                case 't': 
                 ...
         }
}

**Bnorman** · 09-17-2009

Hmm in your code wouldn't "i" be an number value and not a string or char? so it would never pass a "t" to case 't' for output would it?

I was thinking
string ch; //hold the single characters
string word; //hold the user input string
int length; //hold the length of the users string

cin>>word;
length=word.length(); //find the length
ch=word.substr (0,1); // create a loop here to increment until lenght of the string is met

switch (toupper(word[0])) //convert it to upper case so I only have to use capitals in the switch
{
case 'A' : cout <<"Alpha ";
case 'B' : cout <<"Bravo ";
etc...

I really don't know if I am on the right track given my little C++ knowledge

**gamer4life687** · 09-17-2009

Approach the problem first as just a problem. Not as a C++ assignment and your limited amount of coding won't matter.

Why do you need substrings for each character? Look at what I posted again above.

If std::string text = "tree";

What does text[i] refer to.... What is text[0]...

text[0] = 't';
text[1] = 'r';
text[2] = 'e';
text[3] = 'e';

The [] operator returns a char not an integer.

So if i == 0 the
switch(text[i]) would be switch(text[0]) which is a character, in this
case it is the character 't'

**Bnorman** · 09-17-2009

Ah ok... I did not know that... I was only familiar with substr being that it's in the chapter on strings in my textbook. So I was trying to figure out how to use it to get the next character in the user input string. I'll give this a whirl and see if I can get it to work! Thanks for the tips!

**gamer4life687** · 09-17-2009

Np.

Substring is useful when you want to store a string of characters from a larger string. You, however, only need a single character which you can access using [] or .at(). You can store the individual characters if you need to but since your only ouputting, I don't see why you would have too.

**hk_mp5kpdw** · 09-17-2009

Some different ways to loop through a string and do stuff char by char:

Using iterators:

Code:

std::string foo("tree");
for( std::string::const_iterator cit = foo.begin(); cit != foo.end(); ++cit )
{
    std::cout << *cit << std::endl;
}

Using []:

Code:

std::string foo("tree");
std::string::size_type len = foo.length();
for( std::string::size_type cur = 0; cur < len; ++cur )
{
    std::cout << foo[cur] << std::endl;
}

Using .at():

Code:

std::string foo("tree");
std::string::size_type len = foo.length();
for( std::string::size_type cur = 0; cur < len; ++cur )
{
    std::cout << foo.at(cur) << std::endl;
}

All these should output the letters one at a time on separate lines:

Code:

t
r
e
e

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