iterator_range instead of pair for config::child_itors

with this wwe can use .size(), .empty(), .front(), operator bool, etc.
on config::child_itors objects.

src/about.cpp

@@ -150,7 +150,7 @@ void set_about(const config &cfg)
 	for (const config &campaign : cfg.child_range("campaign"))
 	{
 		config::const_child_itors abouts = campaign.child_range("about");
-		if (abouts.first == abouts.second) continue;
+		if (abouts.empty()) continue;
 
 		config temp;
 		std::ostringstream text;

src/config.hpp

@@ -43,6 +43,7 @@
 #include <boost/exception/exception.hpp>
 #include <boost/variant/apply_visitor.hpp>
 #include <boost/variant/variant.hpp>
+#include <boost/range/iterator_range.hpp>
 
 #include "exceptions.hpp"
 #include "tstring.hpp"
@@ -206,8 +207,8 @@ public:
 		Itor i_;
 	};
 
-	typedef std::pair<child_iterator,child_iterator> child_itors;
-	typedef std::pair<const_child_iterator,const_child_iterator> const_child_itors;
+	typedef boost::iterator_range<child_iterator> child_itors;
+	typedef boost::iterator_range<const_child_iterator> const_child_itors;
 
 	/**
 	 * Variant for storing WML attributes.

src/display.cpp

@@ -3400,12 +3400,12 @@ void display::refresh_report(std::string const &report_name, const config * new_
 	SDL_Rect ellipsis_area = rect;
 
 	for (config::const_child_itors elements = report.child_range("element");
-		 elements.first != elements.second; ++elements.first)
+		 elements.begin() != elements.end(); elements.drop_front())
 	{
 		SDL_Rect area = sdl::create_rect(x, y, rect.w + rect.x - x, rect.h + rect.y - y);
 		if (area.h <= 0) break;
 
-		std::string t = (*elements.first)["text"];
+		std::string t = elements.front()["text"];
 		if (!t.empty())
 		{
 			if (used_ellipsis) goto skip_element;
@@ -3431,9 +3431,9 @@ void display::refresh_report(std::string const &report_name, const config * new_
 
 			// check if next element is text with almost no space to show it
 			const int minimal_text = 12; // width in pixels
-			config::const_child_iterator ee = elements.first;
+			config::const_child_iterator ee = elements.begin();
 			if (!eol && rect.w - (x - rect.x + s->w) < minimal_text &&
-				++ee != elements.second && !(*ee)["text"].empty())
+				++ee != elements.end() && !(*ee)["text"].empty())
 			{
 				// make this element longer to trigger rendering of ellipsis
 				// (to indicate that next elements have not enough space)
@@ -3463,7 +3463,7 @@ void display::refresh_report(std::string const &report_name, const config * new_
 				x += area.w;
 			}
 		}
-		else if (!(t = (*elements.first)["image"].str()).empty())
+		else if (!(t = elements.front()["image"].str()).empty())
 		{
 			if (used_ellipsis) goto skip_element;
 
@@ -3503,17 +3503,17 @@ void display::refresh_report(std::string const &report_name, const config * new_
 		}
 
 		skip_element:
-		t = (*elements.first)["tooltip"].t_str().base_str();
+		t = elements.front()["tooltip"].t_str().base_str();
 		if (!t.empty()) {
 			if (!used_ellipsis) {
-				tooltips::add_tooltip(area, t, (*elements.first)["help"].t_str().base_str());
+				tooltips::add_tooltip(area, t, elements.front()["help"].t_str().base_str());
 			} else {
 				// Collect all tooltips for the ellipsis.
 				// TODO: need a better separator
 				// TODO: assign an action
 				ellipsis_tooltip << t;
-				config::const_child_iterator ee = elements.first;
-				if (++ee != elements.second)
+				config::const_child_iterator ee = elements.begin();
+				if (++ee != elements.end())
 					ellipsis_tooltip << "\n  _________\n\n";
 			}
 		}

src/game_data.cpp

@@ -104,7 +104,7 @@ void game_data::set_variable(const std::string& key, const t_string& value)
 config& game_data::add_variable_cfg(const std::string& key, const config& value)
 {
 	std::vector<config> temp = {value};
-	return *get_variable_access_write(key).append_array(temp).first;
+	return get_variable_access_write(key).append_array(temp).front();
 }
 
 void game_data::clear_variable_cfg(const std::string& varname)

src/game_initialization/multiplayer_lobby.cpp

@@ -984,7 +984,7 @@ bool lobby::lobby_sorter::less(int column, const gui::menu::item& row1, const gu
 		return false;
 	}
 
-	config::const_child_iterator gi = list.child_range("game").first, gs = gi;
+	config::const_child_iterator gi = list.child_range("game").begin(), gs = gi;
 	std::advance(gi, row1.id);
 	const config &game1 = *gi;
 	gi = gs;

src/game_initialization/multiplayer_wait.cpp

@@ -302,11 +302,7 @@ void wait::join_game(bool observe)
 			++nb_sides;
 		}
 		if (!side_choice) {
-			size_t count = 0;
-			for(config::child_itors its = get_scenario().child_range("side"); its.second != its.first; ++its.first) {
-				++count;
-			}
-			DBG_MP << "could not find a side, all " << count << " sides were unsuitable\n";
+			DBG_MP << "could not find a side, all " << get_scenario().child_count("side") << " sides were unsuitable\n";
 			set_result(QUIT);
 			return;
 		}
@@ -323,7 +319,7 @@ void wait::join_game(bool observe)
 			if (!era)
 				throw config::error(_("No era information found."));
 			config::const_child_itors possible_sides = era.child_range("multiplayer_side");
-			if (possible_sides.first == possible_sides.second) {
+			if (possible_sides.empty()) {
 				set_result(QUIT);
 				throw config::error(_("No multiplayer sides found"));
 			}

src/gui/core/widget_definition.cpp

@@ -145,7 +145,7 @@ tcontrol_definition::tcontrol_definition(const config& cfg)
 	 * extra header dependencies.
 	 */
 	config::const_child_itors itors = cfg.child_range("resolution");
-	VALIDATE(itors.first != itors.second, _("No resolution defined."));
+	VALIDATE(!itors.empty(), _("No resolution defined."));
 }
 
 } // namespace gui2

src/gui/core/window_builder.cpp

@@ -268,7 +268,7 @@ const std::string& twindow_builder::read(const config& cfg)
 	DBG_GUI_P << "Window builder: reading data for window " << id_ << ".\n";
 
 	config::const_child_itors cfgs = cfg.child_range("resolution");
-	VALIDATE(cfgs.first != cfgs.second, _("No resolution defined."));
+	VALIDATE(!cfgs.empty(), _("No resolution defined."));
 	for(const auto & i : cfgs)
 	{
 		resolutions.push_back(tresolution(i));

src/gui/dialogs/lobby/info.cpp

@@ -136,9 +136,7 @@ bool lobby_info::process_gamelist_diff(const config& data)
 	}
 	DBG_LB << "postdiff " << dump_games_config(gamelist_.child("gamelist"));
 	DBG_LB << dump_games_map(games_by_id_);
-	config::child_itors range = gamelist_.child("gamelist").child_range("game");
-	for(config::child_iterator i = range.first; i != range.second; ++i) {
-		config& c = *i;
+	for(config& c : gamelist_.child("gamelist").child_range("game")) {
 		DBG_LB << "data process: " << c["id"] << " ("
 			   << c[config::diff_track_attribute] << ")\n";
 		int game_id = c["id"];

src/gui/dialogs/unit_advance.cpp

@@ -76,7 +76,7 @@ void tunit_advance::pre_show(twindow& window)
 		// This checks if we've finished iterating over the last unit type advancements
 		// and are into the modification-based advancements.
 		if(i >= last_real_advancement_) {
-			auto iter = sample.get_modifications().child_range("advancement").second;
+			auto iter = sample.get_modifications().child_range("advancement").end();
 			iter--;
 
 			if(iter->has_attribute("image")) {

src/help/help_impl.cpp

@@ -639,8 +639,7 @@ std::vector<topic> generate_trait_topics(const bool sort_generated)
 	{
 		const unit_type &type = i.second;
 		if (description_type(type) == FULL_DESCRIPTION) {
-			config::const_child_itors traits = type.possible_traits();
-			if (traits.first != traits.second) {
+			if (config::const_child_itors traits = type.possible_traits()) {
 				for (const config & trait : traits) {
 					const std::string trait_id = trait["id"];
 					trait_list.insert(std::make_pair(trait_id, trait));

src/help/help_topic_generators.cpp

@@ -391,8 +391,7 @@ std::string unit_topic_generator::operator()() const {
 
 	// Print the possible traits of the unit, cross-reference them
 	// to their respective topics.
-	config::const_child_itors traits = type_.possible_traits();
-	if (traits.first != traits.second) {
+	if (config::const_child_itors traits = type_.possible_traits()) {
 		std::vector<trait_data> must_have_traits;
 		std::vector<trait_data> random_traits;
 
@@ -556,8 +555,8 @@ std::string unit_topic_generator::operator()() const {
 
 	// Generate the movement type of the unit, with resistance, defense, movement, jamming and vision data updated according to any 'musthave' traits which always apply
 	movetype movement_type = type_.movement_type();
-	traits = type_.possible_traits();
-	if (traits.first != traits.second && type_.num_traits() > 0) {
+	config::const_child_itors traits = type_.possible_traits();
+	if (!traits.empty() && type_.num_traits() > 0) {
 		for (const config & t : traits) {
 			if (t["availability"].str() == "musthave") {
 				for (const config & effect : t.child_range("effect")) {

src/scripting/game_lua_kernel.cpp

@@ -1666,10 +1666,10 @@ int game_lua_kernel::impl_game_config_get(lua_State *L)
 
 		//This code for SigurdFD, not the cleanest implementation but seems to work just fine.
 		config::const_child_itors its = game_config_manager::get()->game_config().child_range("era");
-		std::string eras_list((*(its.first))["id"]);
-		++its.first;
-		for(; its.first != its.second; ++its.first) {
-			eras_list = eras_list + "," + (*(its.first))["id"];
+		std::string eras_list(its.front()["id"]);
+		its.drop_front();
+		for(const auto& cfg : its) {
+			eras_list = eras_list + "," + cfg["id"];
 		}
 		return_string_attrib("eras", eras_list);
 	}
@@ -3475,7 +3475,7 @@ int game_lua_kernel::intf_modify_side(lua_State *L)
 			ai::manager::add_ai_for_side_from_file(side_num,switch_ai,true);
 		}
 		// Override AI parameters
-		if (ai.first != ai.second) {
+		if (!ai.empty()) {
 			ai::manager::modify_active_ai_config_old_for_side(side_num,ai);
 		}
 		// Change team color

src/storyscreen/interface.cpp

@@ -40,9 +40,9 @@ void show_story(CVideo& video, const std::string &scenario_name,
 	events::event_context story_context;
 
 	int segment_count = 0;
-	config::const_child_iterator itor = story.first;
+	config::const_child_iterator itor = story.begin();
 	storyscreen::START_POSITION startpos = storyscreen::START_BEGINNING;
-	while (itor != story.second)
+	while (itor != story.end())
 	{
 		storyscreen::controller ctl(video, vconfig(*itor, true),
 			scenario_name, segment_count);
@@ -50,14 +50,14 @@ void show_story(CVideo& video, const std::string &scenario_name,
 
 		switch(result) {
 		case storyscreen::NEXT:
-			if(itor != story.second) {
+			if(itor != story.end()) {
 				++itor;
 				++segment_count;
 				startpos = storyscreen::START_BEGINNING;
 			}
 			break;
 		case storyscreen::BACK:
-			if(itor != story.first) {
+			if(itor != story.begin()) {
 				--itor;
 				--segment_count;
 				startpos = storyscreen::START_END;

src/units/abilities.cpp

@@ -418,8 +418,7 @@ bool unit::ability_affects_self(const std::string& ability,const config& cfg,con
 
 bool unit::has_ability_type(const std::string& ability) const
 {
-	config::const_child_itors itors = this->abilities_.child_range(ability);
-	return itors.first != itors.second;
+	return !abilities_.child_range(ability).empty();
 }
 
 

src/units/animation.cpp

@@ -770,10 +770,10 @@ void unit_animation::add_anims( std::vector<unit_animation> & animations, const
 		anim["apply_to"] = "attack";
 		if (anim["layer"].empty()) anim["layer"] = move_layer;
 		config::const_child_itors missile_fs = anim.child_range("missile_frame");
-		if (anim["offset"].empty() && missile_fs.first == missile_fs.second) {
+		if (anim["offset"].empty() && missile_fs.empty()) {
 			anim["offset"] ="0~0.6,0.6~0";
 		}
-		if (missile_fs.first != missile_fs.second) {
+		if (!missile_fs.empty()) {
 			if (anim["missile_offset"].empty()) anim["missile_offset"] = "0~0.8";
 			if (anim["missile_layer"].empty()) anim["missile_layer"] = missile_layer;
 			config tmp;
@@ -883,7 +883,7 @@ unit_animation::particule::particule(
 {
 	config::const_child_itors range = cfg.child_range(frame_string+"frame");
 	starting_frame_time_=INT_MAX;
-	if(cfg[frame_string+"start_time"].empty() &&range.first != range.second) {
+	if(!range.empty() && cfg[frame_string+"start_time"].empty()) {
 		for (const config &frame : range) {
 			starting_frame_time_ = std::min(starting_frame_time_, frame["begin"].to_int());
 		}

src/units/types.cpp

@@ -723,12 +723,10 @@ const std::string& unit_type::flag_rgb() const {
 bool unit_type::has_random_traits() const
 {
 	if (num_traits() == 0) return false;
-	config::const_child_itors t = possible_traits();
-	while(t.first != t.second) {
-		const config::attribute_value& availability = (*t.first)["availability"];
+	for(const auto& cfg : possible_traits()) {
+		const config::attribute_value& availability = cfg["availability"];
 		if(availability.blank()) return true;
 		if(strcmp(availability.str().c_str(), "musthave") != 0) return true;
-		++t.first;
 	}
 	return false;
 }

src/units/unit.cpp

@@ -519,12 +519,11 @@ unit::unit(const config &cfg, bool use_traits, const vconfig* vcfg)
 	}
 
 	//don't use the unit_type's attacks if this config has its own defined
-	config::const_child_itors cfg_range = cfg.child_range("attack");
-	if(cfg_range.first != cfg_range.second) {
+	if(config::const_child_itors cfg_range = cfg.child_range("attack")) {
 		attacks_.clear();
-		do {
-			attacks_.push_back(attack_type(*cfg_range.first));
-		} while(++cfg_range.first != cfg_range.second);
+		for (const config& cfg : cfg_range) {
+			attacks_.push_back(attack_type(cfg));
+		}
 	}
 
 	//If cfg specifies [advancement]s, replace this [advancement]s with them.
@@ -536,11 +535,9 @@ unit::unit(const config &cfg, bool use_traits, const vconfig* vcfg)
 
 	//don't use the unit_type's abilities if this config has its own defined
 	//Why do we allow multiple [abilities] tags?
-	cfg_range = cfg.child_range("abilities");
-	if(cfg_range.first != cfg_range.second) {
-		this->abilities_.clear();
-		for(const config& abilities : cfg_range)
-		{
+	if (config::const_child_itors cfg_range = cfg.child_range("abilities")) {
+		abilities_.clear();
+		for (const config& abilities : cfg_range) {
 			this->abilities_.append(abilities);
 		}
 	}
@@ -863,7 +860,7 @@ void unit::generate_traits(bool musthaveonly)
 
 	// Now randomly fill out to the number of traits required or until
 	// there aren't any more traits.
-	int nb_traits = std::distance(current_traits.first, current_traits.second);
+	int nb_traits = current_traits.size();
 	int max_traits = u_type.num_traits();
 	for (; nb_traits < max_traits && !candidate_traits.empty(); ++nb_traits)
 	{

src/variable.cpp

@@ -47,7 +47,7 @@ namespace
 		assert(resources::gamedata);
 		config::const_child_itors range = resources::gamedata->get_variable_access_read(varname).as_array();
 
-		if(range.first == range.second)
+		if(range.empty())
 		{
 			return as_nonempty_range_default.child_range("_");
 		}
@@ -224,7 +224,7 @@ size_t vconfig::count_children(const std::string& key) const
 				try
 				{
 					config::const_child_itors range = as_nonempty_range(insert_cfg["variable"]);
-					n += range.second - range.first;
+					n += range.size();
 				}
 				catch(const invalid_variablename_exception&)
 				{
@@ -254,7 +254,7 @@ vconfig vconfig::child(const std::string& key) const
 			try
 			{
 				config::const_child_itors range = as_nonempty_range(insert_cfg["variable"]);
-				return vconfig(*range.first, true);
+				return vconfig(range.front(), true);
 			}
 			catch(const invalid_variablename_exception&)
 			{
@@ -329,7 +329,7 @@ vconfig::all_children_iterator& vconfig::all_children_iterator::operator++()
 
 			config::const_child_itors range = vinfo.as_array();
 
-			if (++inner_index_ < std::distance(range.first, range.second))
+			if (++inner_index_ < int(range.size()))
 			{
 				return *this;
 			}
@@ -380,8 +380,8 @@ vconfig vconfig::all_children_iterator::get_child() const
 		{
 			config::const_child_itors range = as_nonempty_range(vconfig(i_->cfg)["variable"]);
 
-			std::advance(range.first, inner_index_);
-			return vconfig(*range.first, true);
+			range.advance_begin(inner_index_);
+			return vconfig(range.front(), true);
 		}
 		catch(const invalid_variablename_exception&)
 		{

src/variable_info.cpp

@@ -34,10 +34,7 @@ namespace
 	auto get_child_range(TConfig& cfg, const std::string& key, int start, int count) -> decltype(cfg.child_range(key))
 	{
 		auto res = cfg.child_range(key);
-		std::advance(res.first, start);
-		res.second = res.first;
-		std::advance(res.second, count);
-		return res;
+		return { res.begin() + start, res.begin() + start + count};
 	}
 
 	void resolve_negative_value(int size, int& val)