Remove duplicate mapWallet lookups #12276

I think this isn't correct: C syntax A = B = C = D = X sets A,B,C,D to X.. So it assigns wtx to a reference to wtxIn, not to one to mapWallet[hash] as before.

@laanwj the following:

#include <map>
#include <string>
#include <iostream>
using namespace std;
int main() {
  map<int,string> m;
  string s = "hello";
  string& r = m[1] = s;
  r.append(" world");
  cout << s << endl;
  cout << r << endl;
  cout << m[1] << endl;
  return 0;
}

gives:

hello
hello world
hello world

So I think it's correct. I can make it more explicit and still avoid the 2nd lookup.

See http://en.cppreference.com/w/cpp/container/map/operator_at, returns the reference, and the right = expression evaluates to that.

Yes you are correct. Assignment happens from right to left. However I am not really a fan of the multiple assignment per line in this case since we are mixing reverence and value type assigmnents. It's a personal thing I guess but I usually like to separate such logic in multi-line as it helps with debugging etc. The compiler will optimize it anyway :-)

Done.

Good to know, thanks, didn't realize that, but yes it's better to avoid it to avoid confusion. The new formulation is more explicit.