C++ code to HTML (See related posts)

#include <iostream>
#include <string>
#include <fstream>
#include <sstream>
#include <iterator>
using namespace std;

#include <boost/regex.hpp>

const char * expressions =
	// comments
	"(//[^\\n]*|/\\*.*?\\*/)|"
	// precompilers
	"(^[[:blank:]]*#[^\\n]*)|"
	// string literals
	"(\"(?:[^\\\\\"]|\\\\.)*\"|'(?:[^\\\\']|\\\\.)*')|"
	// floating point literal
	"(\\<[[:digit:]]+\\.[[:digit:]]+)|"
	//  integer literal
	"(\\<[[:digit:]]+\\>)|"
	// boolean literal
	"((?:\\<true\\>)|(?:\\<false\\>))|"
	// keywords
	"\\<(__asm|__cdecl|__declspec|__export|__far16|__fastcall|__fortran|__import"
	"|__pascal|__rtti|__stdcall|_asm|_cdecl|__except|_export|_far16|_fastcall"
	"|__finally|_fortran|_import|_pascal|_stdcall|__thread|__try|asm|auto|bool"
	"|break|case|catch|cdecl|char|class|const|const_cast|continue|default|delete"
	"|do|double|dynamic_cast|else|enum|explicit|extern|false|float|for|friend|goto"
	"|if|inline|int|long|mutable|namespace|new|operator|pascal|private|protected"
	"|public|register|reinterpret_cast|return|short|signed|sizeof|static|static_cast"
	"|struct|switch|template|this|throw|true|try|typedef|typeid|typename|union|unsigned"
	"|using|virtual|void|volatile|wchar_t|while)\\>";

const char * format = 
	"(?1<font color = \"#999999\"><i>$&</i></font>)"
	"(?2<font color = \"#000099\">$&</font>)"
	"(?3<font color = \"#009900\">$&</font>)"
	"(?4<font color = \"#996600\">$&</font>)"
	"(?5<font color = \"#999900\">$&</font>)"
	"(?6<font color = \"#660000\"><b>$&</b></font>)"
	"(?7<font color = \"#336699\"><b>$&</b></font>)";

string help = 
	"Usage:"
	"\n\nccode2html <input file> <output file>"
	"\n\nIf output filename is omitted its name it will be <input file>.html";
string code_tag_start = "<PRE>";
string code_tag_end = "</PRE>";

void ccode2html (string input, string output);
string test();

extern const char* pre_expression = "(<)|(>)|(&)|\\r";
extern const char* pre_format = "(?1\\&lt;)(?2\\&gt;)(?3&amp;)";

int main (int argc, char *argv[])
{
	string input_file;
	string output_file;
	if (argc > 3 || argc==1) {
		cout << help;
		exit(0);
	}
	else if (argc==2) {
		input_file=argv[1];
		output_file=input_file+".html";
		ccode2html (input_file, output_file);
	} else {
		input_file=argv[1];
		output_file=argv[2];
		ccode2html (input_file, output_file);
	}
	return 0;
}

// ccode2html method

void ccode2html (string input, string output)
{
	try {
		boost::regex e1, e2;
		e2.assign(pre_expression);
		e1.assign(expressions);
		fstream in (input.c_str(), fstream::in);
		fstream out (output.c_str(), fstream::out);
		out << "<pre>";
		string ins;
		char c;
		while (in.get (c)) {
			ins.append (1, c);
		}
		ostringstream t(std::ios::out | std::ios::binary);
		ostream_iterator<char, char> io(t);
		boost::regex_replace(io, ins.begin(), ins.end(), e2, pre_format, 
				boost::match_default | boost::format_all);
		string s(t.str());
		std::ostream_iterator<char, char> o(out);
		boost::regex_replace(o, s.begin(), s.end(), e1, format,
				boost::match_default | boost::format_all);
		out << "</pre>";
		cout << s;
		cout << input << endl;
		cout << output << endl;
		test();
	} catch (char * exc) {
		cout << "errors:" << endl;
		cout << exc << endl;
	}
}