Single-variable List Comprehension in C++ using Preprocessor Macros

list_comprehension.cpp

/* Single-variable List Comprehension in C++ using Preprocessor Macros
 *
 * (C) Copyright 2011, Mauricio Faria de Oliveira
 * http://mfoliveira.org
 * 
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

#include <iostream>
#include <list>
using namespace std;

/* Pointer to Output Set */
typedef void list_comprehension_set;
list_comprehension_set *list_comprehension_output_set;

/* List-Comprehension Assignment Operator */
template <typename T>
void operator << (list<T> &output_set, list_comprehension_set* &output_set_pointer) {
  
  /* Store output_set's address for the macro. */
  output_set_pointer = (list_comprehension_set *) &output_set;
}

/* List Comprehension */
#define list_comprehension(output_function, variable, input_set, predicate)	\
																			\
list_comprehension_output_set;												\
																			\
{																			\
	typeof((input_set).begin()) iterator = (input_set).begin();				\
	typeof((input_set).front()) variable = *iterator;						\
																			\
	list< typeof(output_function) > *output_set = 							\
		(list< typeof(output_function) > *) list_comprehension_output_set;	\
																			\
	for (;								 									\
		 iterator != (input_set).end();	 									\
	   ++iterator)															\
	{																		\
		variable = *iterator;												\
																			\
		if (predicate)														\
			output_set->push_back(output_function);							\
	}																		\
}

int main(int argc, char** argv) {
  
	/* Input set */
	list<int> input;
	for (int i = 0; i < 5; ++i)
		input.push_back(i);

	/* Output set */
	list<double> output;

	/* List Comprehension */
	output << list_comprehension(3.1415 * x, x, input, x < 3);

	/* Input set contents */
	for (list<int>::iterator it = input.begin();
		 it != input.end();
		 ++it)
		 cout << *it << endl;

	cout << endl;

	/* Output set contents */
	for (list<double>::iterator it = output.begin();
		 it != output.end();
		 ++it)
		 cout << *it << endl;

	return 0;
}