static_cast vs boost::lexical_cast

Question

I am trying to concatenate an integer to a known string, and I have found that there are several ways to do it, two of those being:

int num=13;
string str = "Text" + static_cast<ostringstream*>( &(ostringstream() << num) )->str();

or I could also use boost libraries' lexical_cast:

int num=13;
string str= "Text" + boost::lexical_cast<std::string>(num);

Is the use of boost::lexical_cast more efficient in any way, since I already know the conversion type (int to string)? Or is static_cast just as effective, without having to rely on external libraries?

IMO, `lexical_cast` is much more readable. Note there is also `std::to_string()` in c++11. — hmjd, Jul 22 '13 at 15:11
@KonradRudolph: I originally wrote the cast was unnecessary in my answer (see the edit history), but it appears that operator << returns ostream& even if the RHS is a ostringstream — Armen Tsirunyan, Jul 22 '13 at 18:05
@Armen I know that the cast *itself* is needed but taking the address and casting to *pointer* is convoluted. Just cast to reference. That’s more direct, both syntactically and conceptually. — Konrad Rudolph, Jul 22 '13 at 18:10

score 8 · Accepted Answer · edited May 23 '17 at 12:05

8

string str = "Text" + static_cast<ostringstream*>( &(ostringstream() << num) )->str();

This is ugly and not easily readable. Adding to this the fact that lexical_cast does almost exactly this underneath we can definitely say that using lexical_cast is "better".

In C++11, however, we have to_string overloads.

string str = "Text" + to_string(num);

Which is the best option provided your compiler supports it.

See also How to convert a number to string and vice versa in C++

edited May 23 '17 at 12:05

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answered Jul 22 '13 at 15:14

Armen Tsirunyan

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The cast is needed because the result of `ostringstream() << num` is `ostream&` not `ostringstream&`, so there is no `str()` member. – Mike Seymour Jul 22 '13 at 15:39
@MikeSeymour: Oh, OK, didn't think of it. Editing – Armen Tsirunyan Jul 22 '13 at 15:42

static_cast vs boost::lexical_cast

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