add example for .bind

Author: Fytch

examples/5 bind.cxx

@@ -0,0 +1,53 @@
+#include <ProgramOptions.hxx>
+#include <cstdint>
+#include <vector>
+#include <string>
+#include <iostream>
+#include <string_view>
+
+int main( int argc, char** argv ) {
+	po::parser parser;
+
+	std::uint32_t optimization = 0;	// the value we set here acts as an implicit fallback
+	parser[ "optimization" ]		// corresponds to --optimization
+		.abbreviation( 'O' )		// corresponds to -O
+		.description( "set the optimization level (default: -O0)" )
+		.bind( optimization );		// write the parsed value to the variable 'optimization'
+									// .bind( optimization ) automatically calls .type( po::u32 ) and .single()
+
+	std::vector< std::string > include_paths;
+	parser[ "include-path" ]		// corresponds to --include-path
+		.abbreviation( 'I' )		// corresponds to -I
+		.description( "add an include path" )
+		.bind( include_paths );		// append paths to the vector 'include_paths'
+
+	parser[ "help" ]				// corresponds to --help
+		.abbreviation( '?' )		// corresponds to -?
+		.description( "print this help screen" );
+
+	std::deque< std::string > files;
+	parser[ "" ]					// the unnamed parameter is used for non-option arguments, i.e. gcc a.c b.c
+		.bind( files );				// append paths to the deque 'include_paths
+
+	// parsing returns false if at least one error has occurred
+	if( !parser( argc, argv ) )
+		return -1;
+
+	// we don't want to print anything else if the help screen has been displayed
+	if( parser[ "help" ].was_set() ) {
+		std::cout << parser << '\n';
+		return 0;
+	}
+
+	// print the parsed values
+	// note that we don't need to access parser anymore; all data is stored in the bound variables
+	std::cout << "optimization level = " << optimization << '\n';
+
+	std::cout << "include files (" << files.size() << "):\n";
+	for( auto&& i : files )
+		std::cout << '\t' << i << '\n';
+
+	std::cout << "include paths (" << include_paths.size() << "):\n";
+	for( auto&& i : include_paths )
+		std::cout << '\t' << i << '\n';
+}