In file ../../src/Pegasus/Common/String.h:

PEGASUS_COMMON_LINKAGE String operator+

(const String& str1,
  const String& str2)

This overload operator (+) concatenates String objects.

Documentation

This overload operator (+) concatenates String objects. For example, 
        String t1 = "abc";
        String t2;
        t2 = t1 + "def"
        assert(t2 == "abcdef");

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