diff --git a/built_in_type_conversion.cpp b/built_in_type_conversion.cpp
new file mode 100644
index 0000000..8959f36
--- /dev/null
+++ b/built_in_type_conversion.cpp
@@ -0,0 +1,68 @@
+/* Check cf5-opt.vim defs.
+VIM: let g:lcppflags="-std=c++11 -O2 -pthread"
+VIM: let g:wcppflags="/O2 /EHsc /DWIN32"
+VIM: let g:cppflags=g:Iboost.g:Itbb
+VIM: let g:ldflags=g:Lboost.g:Ltbb.g:tbbmalloc.g:tbbmproxy
+VIM: let g:ldlibpath=g:Bboost.g:Btbb
+VIM: let g:argv=""
+VIM-: let g:cf5output=0
+*/
+#include <iostream>
+#include <exception>
+
+void prom( long long )
+{
+	std::cout << "prom" << std::endl;
+}
+
+void fpprom( double )
+{
+	std::cout << "fpprom" << std::endl;
+}
+
+void integral( short )
+{
+	std::cout << "integral" << std::endl;
+}
+
+void conv_double( float )
+{
+	std::cout << "conv_double" << std::endl;
+}
+
+void fpint( int )
+{
+	std::cout << "fpint" << std::endl;
+}
+
+void fpint2( float )
+{
+	std::cout << "fpint2" << std::endl;
+}
+
+int main ( void )
+{try{
+
+	prom( short(10) );
+	fpprom( float(1.) );
+	integral( int(100000) );
+	conv_double( double(10ll) );
+	fpint( float(1.) );
+	fpint( double(2.) );
+	fpint2( int(2) );
+
+	return 0;
+}
+catch ( const std::exception& e )
+{
+	std::cerr << std::endl
+			<< "std::exception(\"" << e.what() << "\")." << std::endl;
+	return 2;
+}
+catch ( ... )
+{
+	std::cerr  << std::endl
+			<< "unknown exception." << std::endl;
+	return 1;
+}}
+