Optimal method to create a large string containing several variables?
I want to create a string that contains many variables:
std::str开发者_JS百科ing name1 = "Frank";
std::string name2 = "Joe";
std::string name3 = "Nancy";
std::string name4 = "Sherlock";
std::string sentence;
sentence = name1 + " and " + name2 + " sat down with " + name3;
sentence += " to play cards, while " + name4 + " played the violin.";
This should produce a sentence that reads
Frank and Joe sat down with Nancy to play cards, while Sherlock played the violin.
My question is: What is the optimal way to accomplish this? I am concerned that constantly using the + operator is ineffecient. Is there a better way?
Yes, std::stringstream
, e.g.:
#include <sstream>
...
std::string name1 = "Frank";
std::string name2 = "Joe";
std::string name3 = "Nancy";
std::string name4 = "Sherlock";
std::ostringstream stream;
stream << name1 << " and " << name2 << " sat down with " << name3;
stream << " to play cards, while " << name4 << " played the violin.";
std::string sentence = stream.str();
You could use boost::format for this:
http://www.boost.org/doc/libs/1_41_0/libs/format/index.html
std::string result = boost::str(
boost::format("%s and %s sat down with %s, to play cards, while %s played the violin")
% name1 % name2 % name3 %name4
)
This is is a very simple example of what boost::format can do, it is a very powerful library.
You can call member functions like operator+=
on temporaries. Unfortunately, it has the wrong associativity, but we can fix that with parenthesis.
std::string sentence(((((((name1 + " and ")
+= name2) += " sat down with ")
+= name3) += " to play cards, while ")
+= name4) += " played the violin.");
It's a little ugly, but it doesn't involve any unneeded temporaries.
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