C++ Explicit Conversion Constructor

Question

I am trying to implement an explicit conversion constructor for an assignment and I am confused what is it I am required to do. I have a WordList containing a single element, and am to make this constructor explicit so I cannot do:

WordList myList;
list = 'i'; // error

That's assignment (but with a typo in the names) not construction — Flexo, Mar 20 '12 at 16:37
possible duplicate of [What does the explicit keyword in C++ mean?](http://stackoverflow.com/questions/121162/what-does-the-explicit-keyword-in-c-mean) — , Mar 20 '12 at 16:38
This question is too vague. What does "assigning a word to a world-_list_" mean? Then you have not shown your definition of WordList. Then, 'i' is not a string, but a char. My best advice: Before diving into advanced topics, first learn the basics. — Sebastian Mach, Mar 20 '12 at 16:38
Have a member function: 'Wordlist& operator= ( cons char* c );' — Akanksh, Mar 20 '12 at 16:38
@Akanksh: He's assigning chars and he wants to specifically _forbid_ that. I think the question is too vague anyways. — Sebastian Mach, Mar 20 '12 at 16:40
The only assignment operator I have for WordList is '='. Sorry, I am not clear on my terminology as I am taking C++ for the first time. — Jon, Mar 20 '12 at 16:42
@phresnel : Interesting, now that you mention it, I am not quite sure what he/she is asking. Is it assignment operator? disable assignment operator? Ctor? Explicit Cotr? — Akanksh, Mar 20 '12 at 16:42
@user1277607: Imho, that is really not a clean design. What does it mean to initialize a list-of-words with a letter? To me, this smells like there is a [god-object](http://en.wikipedia.org/wiki/God_class) or [feature-creep](http://en.wikipedia.org/wiki/Feature_creep) growing up. — Sebastian Mach, Mar 20 '12 at 16:57

score 8 · Accepted Answer · answered Mar 20 '12 at 16:37

8

All that you need to use explicit keyword as:

class WordList 
{
   explicit WordList(char c) {}
};

WordList w = 'i';  //error
WordList v ('i') ; //ok

answered Mar 20 '12 at 16:37

Nawaz

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I tried placing the keyword explicit in front of my constructor in both my .cpp and .h file, but I received the error "illegal storage class". I can't post my code up here incase my prof sees it. – Jon Mar 20 '12 at 16:39
@user1277607: No. Do that only in .`h` file, in the declaration only. In my example, I defined it in the class itself, so `explicit` is allowed here in this case (in the definition). – Nawaz Mar 20 '12 at 16:40

C++ Explicit Conversion Constructor

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