How to convert std::string to upper case?

Question

I want to convert a std::string to uppercase. I am aware of the function toupper(), however in the past I have had issues with this function and it is hardly ideal anyway as use with a string would require iterating over each character.

Is there an alternative which works in correct manner of the time?

How could converting a sequence of characters to uppercase possibly not involve iterating over those characters? — , Feb 09 '18 at 17:54
And why would the functionality NOT ALREADY BE THERE instead of having to recreate the wheel all the time. ISNUMERIC and REPLACE being two other recent examples I've run into. — David, Dec 12 '18 at 20:18

Jarod42 · Accepted Answer · 2019-03-21T18:16:21.700

2

std::toupper has several overloads

template <class charT> charT toupper(charT, const locale&)
int toupper(int ch)

So taking its address might be complicated.

You might use lambda to let compiler found the right overload:

(In addition, as char might be signed or not, and toupper expects unsigned char value (or EOF))

std::transform(s.begin(), s.end(), s.begin(),
               [](unsigned char c){ return std::toupper(c); });

edited Mar 21 '19 at 18:16

answered Feb 09 '18 at 17:53

Jarod42

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_"as use with a string would require iterating over each character."_ Same same here, with cream, candy and syrup. – Feb 09 '18 at 17:56

How to convert std::string to upper case?

1 Answers1