'+' cannot add two pointers error

Question

I can do what the following code shows:

std::string a = "chicken ";
std::string b = "nuggets";
std::string c = a + b;

However, this fails:

std::string c = "chicken " + "nuggets";

It gives me an error saying " '+' cannot add two pointers". Why is that so? Is there an alternative way to do this without getting an error?

I thought I had explained the question correctly, sorry. And no, I don't need to include . — Vicente Bermúdez, May 18 '15 at 15:15
@VicenteBermúdez If you're using `std::string`, then you *do* need to `#include `. Without it, code might happen to partially work if some of the required definitions are brought in by other headers, but that does't mean you don't need to include it. Expect weird errors popping up later if you don't. — Angew is no longer proud of SO, May 18 '15 at 15:16
for std::strings additive operator is overloaded to concatenate the two input strings. However "chicken " and "nuggets " are C-strings. the compiler does not concatenate them. — 911, May 18 '15 at 15:18

Jarod42 · Accepted Answer · 2016-01-28T12:32:15.857

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"chicken " and "nuggets" are literal C-string and not std::string.

You may concatenate directly with:

std::string c = "chicken " "nuggets";

Since C++14, you may add suffix s to have string

using namespace std::string_literals;
std::string c = "chicken "s + "nuggets"s;

edited Jan 28 '16 at 12:32

answered May 18 '15 at 15:16

Jarod42

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For google sake, this is the answer for exercise 1-2 in "Accelerated C++" (Koenig, 2000). – MordechayS Nov 14 '17 at 10:43

score 6 · Answer 2 · answered May 18 '15 at 15:16

"chicken " and "nuggets" are not of type std::string but are const char[]. As such even though you want to assign the concatenation to a string they types don't have an operator +. You could solve this using:

std::string c = std::string("chicken ") + "nuggets";

Hcorg · Answer 3 · 2015-05-18T15:24:15.287

4

Both "chicken" and "nuggets" has type const char* (as literals in code). So you are trying to add to pointers.

Try std::string c = std::string("chicken") + "nuggets";

std::string is not part of language itself, it's a part of standard library. C++ aims to have as few language features as possible. So built-in type for strings is not present in parser etc. That's why string literals will be treaded as pointers.

EDIT

To be completely correct: type of literals is really const char[N] (where N is character count in literal +1 for \0. But in C++ arrays ([]) can be treated as pointers, and that is what compiler tries to do (as it cannot add arrays)

edited May 18 '15 at 15:24

answered May 18 '15 at 15:18

Hcorg

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Note that the types are actually `const char[9]` and `const char[8]`. – juanchopanza May 18 '15 at 15:19
true, I wanted to simplify answer (without explaining that [] in C++ is implicitly a pointer :) ) – Hcorg May 18 '15 at 15:20
see [this](http://stackoverflow.com/questions/12517983/c-what-is-the-datatype-of-string-literal) on why – NathanOliver May 18 '15 at 15:21

'+' cannot add two pointers error

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