dat/clua/iter.lua: iterators for Lua.

Currently only includes:

rectangle_iterator: iterates points between two corners.
los_iterator: iterates over currently visible points in LOS.
adjacent_iterator: iterates over adjacent points to the center.

Most iterators accept a "filter" parameter that is a function which
should either return true if the point is acceptable for the iteration,
or false if it is not.

los_iterator is currently restricted to player LOS rather than actor or
monster LOS, but could be expanded at a later date.

All of the iterators seem to work as intended: hopefully I haven't made
too many mistakes with them.

2 files changed, 177 insertions, 0 deletions

diff --git a/crawl-ref/source/clua.cc b/crawl-ref/source/clua.cc
index 4f25a2d362..d750fc9f09 100644
--- a/crawl-ref/source/clua.cc
+++ b/crawl-ref/source/clua.cc
@@ -636,6 +636,7 @@ void CLua::init_lua()
     lua_register(_state, "require", _clua_require);
 
     execfile("clua/util.lua", true, true);
+    execfile("clua/iter.lua", true, true);
     execfile("clua/init.lua", true, true);
 
     if (managed_vm)
diff --git a/crawl-ref/source/dat/clua/iter.lua b/crawl-ref/source/dat/clua/iter.lua
new file mode 100644
index 0000000000..9972a1208c
--- /dev/null
+++ b/crawl-ref/source/dat/clua/iter.lua
@@ -0,0 +1,176 @@
+------------------------------------------------------------------------------
+-- iter.lua:
+-- Iterationeering functions.
+------------------------------------------------------------------------------
+--
+-- Example usage of adjacent_iterator:
+--
+-- function iter.rats()
+--   local i
+--   for i in iter.adjacent_iterator() do
+--     dgn.create_monster(i.x, i.y, "rat")
+--   end
+-- end
+--
+-- The above function will surround the player with rats.
+--
+------------------------------------------------------------------------------
+-- dgn.point iterators.
+-- All functions expect dgn.point parameters, and return dgn.points.
+------------------------------------------------------------------------------
+iter = {}
+
+------------------------------------------------------------------------------
+-- rectangle_iterator
+------------------------------------------------------------------------------
+iter.rectangle_iterator = {}
+
+function iter.rectangle_iterator:_new ()
+  local m = {}
+  setmetatable(m, self)
+  self.__index = self
+  return m
+end
+
+function iter.rectangle_iterator:new (corner1, corner2, filter)
+  if corner1 == nil or corner2 == nil then
+    error("need two corners to a rectangle")
+  end
+
+  if corner2.x < corner1.x then
+    error("corner2's x less than corner1's; did you swap them?")
+  elseif corner2.y < corner1.y then
+    error("corner2's y less than corner1's; did you swap them?")
+  end
+
+  local mt = iter.rectangle_iterator:_new()
+  mt.min_x = corner1.x
+  mt.min_y = corner1.y
+  mt.max_x = corner2.x
+  mt.max_y = corner2.y
+  mt.cur_x = corner1.x - 1
+  mt.cur_y = corner1.y
+  mt.filter = filter or nil
+
+  return mt:iter()
+end
+
+function iter.rectangle_iterator:next()
+  local point = nil
+  repeat
+    if self.cur_x >= self.max_x then
+      self.cur_y = self.cur_y + 1
+      self.cur_x = self.min_x
+      if self.cur_y > self.max_y then
+        point = -1
+      else
+        point = dgn.point(self.cur_x, self.cur_y)
+        if not self:check_filter(point) then
+          point = -2
+        end
+      end
+    else
+      self.cur_x = self.cur_x + 1
+      point = dgn.point(self.cur_x, self.cur_y)
+      if not self:check_filter(point) then
+        point = -2
+      end
+    end
+    if point == -1 then
+      return nil
+    elseif point == -2 then
+      point = nil
+    end
+  until point
+
+  return point
+end
+
+function iter.rectangle_iterator:check_filter(point)
+  if self.filter ~= nil then
+    if self.filter(point) then
+      return true
+    else
+      return false
+    end
+  else
+    return true
+  end
+end
+
+function iter.rectangle_iterator:iter ()
+  return function() return self:next() end, nil, nil
+end
+
+function iter.rect_iterator(top_corner, bottom_corner, filter)
+  return iter.rectangle_iterator:new(top_corner, bottom_corner, filter)
+end
+
+-------------------------------------------------------------------------------
+-- los_iterator
+-------------------------------------------------------------------------------
+
+function iter.los_iterator (include_center, filter, center)
+  local y_x, y_y
+  if center == nil then
+    y_x, y_y = you.pos()
+  else
+    y_x, y_y = center:xy()
+  end
+  local top_corner = dgn.point(y_x - 8, y_y - 8)
+  local bottom_corner = dgn.point(y_x + 8, y_y + 8)
+  local function check_los (point)
+    local _x, _y = point:xy()
+
+    if filter ~= nil then
+      if not filter(point) then
+        return false
+      end
+    end
+
+    if include_center == true and y_x == _x and y_y == y then
+      return true
+    else
+      return false
+    end
+
+    if you.see_cell(_x, _y) then
+      return true
+    else
+      return false
+    end
+
+  end
+  return iter.rect_iterator(top_corner, bottom_corner, check_los)
+end
+
+-------------------------------------------------------------------------------
+-- adjacent_iterator
+-------------------------------------------------------------------------------
+
+function iter.adjacent_iterator (include_center, filter, center)
+  local y_x, y_y
+  if center == nil then
+    y_x, y_y = you.pos()
+  else
+    y_x, y_y = center:xy()
+  end
+  local top_corner = dgn.point(y_x - 1, y_y - 1)
+  local bottom_corner = dgn.point(y_x + 1, y_y + 1)
+  local function check_adj (point)
+    local _x, _y = point:xy()
+
+    if filter ~= nil then
+      if not filter(point) then
+        return false
+      end
+    end
+
+    if include_center ~= true and y_x == _x and y_y == y then
+      return false
+    end
+
+    return true
+  end
+  return iter.rect_iterator(top_corner, bottom_corner, check_adj)
+end