C++ で `std::string in` に対する `in == "http" or in "https"` 的なパターンとコストの比較 ref: http://qiita.com/usagi/items/718f573e27dd599c32e6

file0.cpp

in == "http" or in == "https"

file1.cpp

  auto f =
  [] ( auto g )
  { auto t0 = std::chrono::steady_clock::now();
    g();
    std::cout << ( std::chrono::steady_clock::now() - t0 ).count() << ' ';
  };

file2.cpp

      // for reference
      f( [ ]{ return true; } );
      // for reference
      f( [&]{ return in == "http"; } );
      // 1. simple eq-or pattern
      f( [&]{ return in == "http" or in =="https"; } );
      // 2. substr-eq pattern
      f( [&]{ return in.substr( 0, 4 ) == "http"; } );
      // 3. size-strcmp pattern
      f( [&]{ return in.size() > 3 and std::strcmp( "http", in.c_str() ); } );
      // 4. find pattern
      f( [&]{ return in.find( "http" ) == 0; } );
      // 5. boost::xpressive pattern
      f( [&]{ using namespace boost::xpressive; smatch r; sregex p = bos >> as_xpr( "http" ) >> ( ! as_xpr( 's' ) ) >> eos; return regex_match( in, r, p ); } );

file3.cpp

#include <iostream>
#include <string>
#include <chrono>
#include <boost/xpressive/xpressive.hpp>

auto main() -> int
{
  auto f =
  [] ( auto g )
  { auto t0 = std::chrono::steady_clock::now();
    g();
    std::cout << ( std::chrono::steady_clock::now() - t0 ).count() << ' ';
  };

  using namespace std::literals::string_literals;

  for ( const auto& in : { "https"s, "https@https@https@https@https@https@https@https@https@https@https@https@https@https@https@https@"s } )
  {
    for ( auto n = 0; n < 8; ++n )
    {
      // for reference
      f( [ ]{ return true; } );
      // for reference
      f( [&]{ return in == "http"; } );
      // 1. simple eq-or pattern
      f( [&]{ return in == "http" or in =="https"; } );
      // 2. substr-eq pattern
      f( [&]{ return in.substr( 0, 4 ) == "http"; } );
      // 3. size-strcmp pattern
      f( [&]{ return in.size() > 3 and std::strcmp( "http", in.c_str() ); } );
      // 4. find pattern
      f( [&]{ return in.find( "http" ) == 0; } );
      // 5. boost::xpressive pattern
      f( [&]{ using namespace boost::xpressive; smatch r; sregex p = bos >> as_xpr( "http" ) >> ( ! as_xpr( 's' ) ) >> eos; return regex_match( in, r, p ); } );
      std::cout << '\n';
    }
    std::cout << '\n';
  }
}

file4.txt

593 5884 3070 507 190 5990 71745 
190 365 268 277 190 260 7513 
177 220 262 258 190 228 5702 
178 220 262 250 190 227 5447 
178 220 262 250 190 227 5318 
175 223 263 257 190 227 5275 
175 220 263 257 190 228 5272 
175 220 262 258 190 227 5300 

178 220 262 273 187 228 5325 
178 220 262 250 190 228 5272 
175 220 263 250 190 228 5237 
175 220 262 250 190 228 5245 
175 220 262 250 190 228 5252 
177 220 265 253 187 227 5238 
175 220 263 250 190 227 5240 
178 220 263 252 190 228 5282