! FOLLOWER: an Inform library by Andrew Clover, release 3

!--------------------------------------------------------------------------
! FOLLOWER: an Inform library by Andrew Clover, release 3
! Based on Gareth Rees's original code.
! Updated by Gareth Rees, and then modified for use with Inform 6 by
! Neil Brown.
!
! An Inform library to allow things to be FOLLOWed. To use, `Include' it
! just after `verblib', then give any object that can be followed `class
! followclass'. To move a followable object, call MoveNPC(object,
! destination, actiontomove, objectnumber). Pass 0 for objectnumber to
! disallow following. Pass 0 for destination to remove object.
!
! When the player attempts to follow the object, the action <actiontomove
! objectnumber> will be generated.
!
! In this release, the player can also attempt to follow any followable
! object contained within the moving followable object. For example, if
! Louise drives off in a car, the player may 'Follow Louise' as well as
! 'Follow car'.
!
! Examples: MoveNPC(bob, bobshouse, ##Go, n_obj);
! MoveNPC(driver, car, ##Enter, car);
!--------------------------------------------------------------------------

Property follow_action 0;
Property follow_object 0;
Attribute followable;

Class followclass
with follow_action 0,
follow_object 0,
has followable;

[ NewRoom i;
objectloop (i has followable)
{ if (i~=followclass) i.follow_object=0;
}
rfalse;
];

[ FollowScope i;
if (scope_stage==1) rfalse;
if (scope_stage==2)
{
objectloop (i ofclass followclass)
{ PlaceInScope(i);
}
rtrue;
}
"Go where?";
];

[ FollowSub oldnoun oldpos;
if (parent(noun) == location or player)
print_ret "You are already with ", (the) noun, ".";
if (noun hasnt followable)
"That's not something you can follow.";
if (noun.follow_object == 0) {
print "You don't know where ";
if (noun has animate) {
if (noun has female) print "she"; else print "he";
} else print "that";
" is.";
}
oldnoun = noun;
oldpos = parent(player);
<(noun.follow_action) noun.follow_object>;
if (oldnoun notin parent(player) && parent(player) ~= oldpos)
print "^(", (the) oldnoun, " doesn't seem to be here any more.)^";
rtrue;
];

[ MoveNPC tomove dest actn objn;
if (dest==parent(player))
tomove.follow_action= 0;
else
if (parent(tomove)==parent(player))
MoveNPC2(tomove, actn, objn);
if (dest==0) remove tomove;
else move tomove to dest;
];

[ MoveNPC2 tomove actn objn i;
if (tomove has followable) {
tomove.follow_action= actn;
tomove.follow_object= objn;
objectloop(i in tomove) {
MoveNPC2(i, actn, objn);
}
}
];

Verb "follow" "chase" "pursue" "trail"
* scope=FollowScope -> Follow;