Implement monster_iterator.

monster_iterator allows iterating over live monsters in
env.mgrid, possibly subject to some location/visibility
restrictions.

Possible restrictions:
- within some radius (circle_def::contains(mon->pos())
- position inside some LOS (los_def::see_cell(mon->pos())
- visible to some actor (actor::can_see(mon))

Sample use:

for (int i = 0; i < MAX_MONSTERS; ++i)
{
    monsters* const monster = &menv[i];
    if (!monster->alive())
        continue;
    // ...

// becomes

for (monster_iterator mi; mi; ++mi)
{
    // ..., replacing monster-> by mi->
    //      and monster by *mi

If you were checking for mons_near(monster), use
    monster_iterator mi(&you.get_los());
if you were checking for you.can_see(monster), use
    monster_iterator mi(&you);
if you were checking for
(monster->pos()-you.pos()).abs() <= r*r+1, use
    monster_iterator mi(circle_def(you.pos(), r, C_ROUND)).

This is not as general as one might hope, but it should
allow reducing the amount of code that knows how monsters
are stored.

1 files changed, 1 insertions, 0 deletions

diff --git a/crawl-ref/source/makefile.obj b/crawl-ref/source/makefile.obj
index c85450cd5f..ccbfb75aeb 100644
--- a/crawl-ref/source/makefile.obj
+++ b/crawl-ref/source/makefile.obj
@@ -103,6 +103,7 @@ mon-behv.o \
 mon-cast.o \
 mon-gear.o \
 mon-info.o \
+mon-iter.o \
 mon-pick.o \
 mon-util.o \
 monplace.o \