Convert first letter in string to uppercase

Question

I have a string: "apple". How can I convert only the first character to uppercase and get a new string in the form of "Apple"?

I can also have a string with multibyte characters.

What if the first character of the string is a multibyte character ?

Evangelista

google.com/search?q=Title+case+a+string – Hardpan

The language I'm using is C++ – Evangelista

google.com/search?q=Title+case+string+c%2B%2B – Hardpan

Amazing this isn't a duplicate. – Hardpan

@RobertHarvey I suppose we can't mark 'convert char to uppercase' as a duplicate? – Lancelancelet

This is a tricky thing to do in a completely general way. It requires specific knowledge of the encoding, a precise definition of "character", and sometimes even knowing the culture/language of the (part of the) string you're modifying. You'll almost certainly need some amount of library help. – Interfuse

Answer 1

string str = "something";
str[0] = toupper(str[0]);

That's all you need to do. It also works for C strings.

Overturf

Do you mean char* str = "something"; str[0] = toupper(str[0]); would work? (as this is c-string). – Dunbarton

@Nawaz not that because that would be modifying a const char[9] (in memory you can't modify). But if you had a C string in some memory you own then yes it will work. – Overturf

Answer 2

Like what Carneigie said,

string str = "something";
str[0] = toupper(str[0]);

but also remember to:

#include <string>
#include <cctype>

all the way up

Em

I don't understand. Why do we need to include cctype? This is a C header, and it's best practise to stick with C++ headers only with C++. Also, the code above doesn't require cctype. ??? – Strachey

@Strachey It's for C++　ａｓ　ｗｅｌｌ．　cplusplus.com/reference/cctype　touppeｒ　ｒｅｑｕｉｒｅｓ　ｃｃｔｙｐｅ – Em

Answer 3

I cannot use str[0] because, I can have string which has multibyte characters

I don't know of any CRT implementation that supports non-ASCII character classification and conversion. If you want to support Unicode then everything is much more complicated since "converting the first character to uppercase" may be meaningless in other languages. You have to use a Unicode library written by experts for this.

To illustrate how complicated it is, consider the following case in English. Converting the three code-point sequence 'file' (with f-i ligature) shall break the first codepoint into two separate letters resulting in 'File'. Please note that the standard C/C++ interfaces for doing case classification and conversion don't take such cases into account, so it's even impossible to implement them to support Unicode correctly.

Parliamentarian

Answer 4

#include <iostream>
using namespace std;

void capitalize (string &s)
{
    bool cap = true;

    for(unsigned int i = 0; i <= s.length(); i++)
    {
        if (isalpha(s[i]) && cap == true)
        {
            s[i] = toupper(s[i]);
            cap = false;
        }
        else if (isspace(s[i]))
        {  
            cap = true;
        }
    }
}

Biltong

Perfect, just what I was looking for. This also takes multiple words with spaces. – Chickadee

Answer 5

(Only works with 'ASCII' characters.)

std::wstring s = L"apple";

if(islower(s.at(0) <= 'z' ? s.at(0) : 'A'))
    s[0] += 'A' - 'a';

---

Or if you are feeling fancy and feel like torturing any future readers of your code:

std::wstringstream wss;
wss << std::uppercase   << s[0]
    << std::nouppercase << s.substr(1);
wss >> s;

Lancelancelet

I cannot use str[0] because, I can have string which has multibyte characters – Evangelista

The fancy form is rather ugly and slow. Better warn him NOT to do this way. – Dunbarton

I don't think this will work with multibyte characters because adding 'A' - 'a' won't necessarily convert some multibyte character to uppercase. It will only work for ASCII, no? – Overturf

@SethCarnegie Indeed. To be specific, Latin-1 only. What about the second piece of code, though? – Lancelancelet

No idea, never dealt with multibyte strings before. – Overturf

std::uppercase does not what you think it does. According to en.cppreference.com/w/cpp/io/manip/uppercase it only works in floating-point and hexadecimal integer output – Rouen