Finding Last character in c++ string

[HeaterUp]

Hello everyone, I am currently making a program right now in c++ that I need to be able to find the last character in a c++ string and I was looking for if there was any operations in the string library to do that. If I can't do that I would like to search through a user inputted string for a certain letter these are the two options I have thought of to tackle the task. I am limiting myself to where I am not able to use <cstdlib>, any structs, or pointers so keep that in mind.

Thanks for any answers.

[fizzlesticks]

http://www.cplusplus.com/reference/string/string/back/

[Mira Yurizaki]

9 minutes ago, HeaterUp said:

Hello everyone, I am currently making a program right now in c++ that I need to be able to find the last character in a c++ string and I was looking for if there was any operations in the string library to do that. If I can't do that I would like to search through a user inputted string for a certain letter these are the two options I have thought of to tackle the task. I am limiting myself to where I am not able to use <cstdlib>, any structs, or pointers so keep that in mind.

Thanks for any answers.

Barring the back function, a well formed string should have a null terminator. Otherwise you could look for a newline character, assuming the user presses enter to input the text.

[HeaterUp]

33 minutes ago, M.Yurizaki said:

Barring the back function, a well formed string should have a null terminator. Otherwise you could look for a newline character, assuming the user presses enter to input the text.

Follow up question I'm now realizing ill need the first character as well.

[OhadShwartzman]

1 minute ago, HeaterUp said:

Follow up question I'm now realizing ill need the first character as well.

string[0] will bring you the first character.

[HeaterUp]

1 minute ago, NoGravityPanda said:

string[0] will bring you the first character.

Thank you very much 

[Unimportant]

8 hours ago, M.Yurizaki said:

Barring the back function, a well formed string should have a null terminator. Otherwise you could look for a newline character, assuming the user presses enter to input the text.

There's nothing in the pre C++ 11 standard that says a std::string has to include a 0-terminator.The C string returned by std::string::c_str() includes the 0-terminator ofc, but that does not mean the actual (implementation defined) representation of the string inside std::string includes it. Thus:

std::string Foo("Bar");

//Foo[3] is not guaranteed to be 0, in fact, it could be undefined behavior (out of bounds access).

C++11 has new requirements for std::string that imply 0-termination, but even then it is a bad idea to look for a 0-terminator in a std::string for the reason that it is perfectly legal for a std::string to contain 0-characters (that are NOT the end of the string).

 

Inputting a string using streams does not store the newline in the string.

 

@HeaterUp

Accessing the last character:

//C++11
char LastChar = Foo.back();

//In C++03, std::string::back is missing, but one can use reverse iterator begin (this works in C++11 too, ofc:
char LastChar = *Foo.rbegin();

Accessing the first character:

//C++11
char FirstChar = Foo.front();

//In C++03, std::string::front is missing, but one can use iterator begin (this works in C++11 too, ofc:
char FirstChar = *Foo.begin();

Take care to guard against doing this on empty strings.

[Mira Yurizaki]

3 hours ago, Unimportant said:

There's nothing in the pre C++ 11 standard that says a std::string has to include a 0-terminator.The C string returned by std::string::c_str() includes the 0-terminator ofc, but that does not mean the actual (implementation defined) representation of the string inside std::string includes it. Thus:

std::string Foo("Bar");

//Foo[3] is not guaranteed to be 0, in fact, it could be undefined behavior (out of bounds access).

C++11 has new requirements for std::string that imply 0-termination, but even then it is a bad idea to look for a 0-terminator in a std::string for the reason that it is perfectly legal for a std::string to contain 0-characters (that are NOT the end of the string).

So basically C++ added proper string functionality.

[Unimportant]

12 minutes ago, M.Yurizaki said:

So basically C++ added proper string functionality.

I don't see how it was not proper before. std::string encapsulates the string as any object should. You can get the string's length trough a member function, you don't and should not manually look for the end. The internal representation of the string is the STL developer's problem, not yours. Once you request a C style string trough std::string::c_str() the 0-terminator is there but that function's sole use is to interface with C functions, such as a library, and should never be used for any other reason imho.

 

I kinda like the fact that std::getline reads an entire line from, for example, a file, even if that line happens to contain a 0-character and can return it in a std::string. That, and similar functionality, would not be possible if we had to sacrifice 0 as a termination character for a self contained object that can keep track of it's own length internally anyway.

[Mira Yurizaki]

1 minute ago, Unimportant said:

I don't see how it was not proper before. std::string encapsulates the string as any object should. You can get the string's length trough a member function, you don't and should not manually look for the end. The internal representation of the string is the STL developer's problem, not yours. Once you request a C style string trough std::string::c_str() the 0-terminator is there but that function's sole use is to interface with C functions, such as a library, and should never be used for any other reason imho.

 

I kinda like the fact that std::getline reads an entire line from, for example, a file, even if that line happens to contain a 0-character and can return it in a std::string. That would not be possible if we had to sacrifice 0 as a termination character for a self contained object that can keep track of it's own length internally anyway.

What I'm saying is C++ treats strings as something more like a data type than borrowing off another one with special rules.