From 9048dbd9aed2867a4af78cd5e002dc4fcd223bf2 Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Sat, 10 Oct 2020 10:19:26 -0400
Subject: [PATCH 01/28] Added pickup and drop functions

---
 src/objects.jl | 32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/src/objects.jl b/src/objects.jl
index d5eaa2b..03700a5 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -51,6 +51,11 @@ const TURN_LEFT = TurnLeft()
 #####
 
 abstract type AbstractObject end
+abstract type Item <: AbstractObject end
+
+# Placeholder for empty inventory
+struct Null <: Item end
+const NULL = Null()
 
 Base.show(io::IO, x::AbstractObject) = print(io, Crayon(foreground=get_color(x), reset=true), convert(Char, x))
 
@@ -74,12 +79,12 @@ Door(c) = Door{c}()
 Base.convert(::Type{Char}, ::Door) = '⩎'
 get_color(::Door{C}) where C = C
 
-struct Key{C} <: AbstractObject end
+struct Key{C} <: Item end
 Key(c) = Key{c}()
 Base.convert(::Type{Char}, ::Key) = '⚷'
 get_color(::Key{C}) where C = C
 
-struct Gem <: AbstractObject end
+struct Gem <: Item end
 const GEM = Gem()
 Base.convert(::Type{Char}, ::Gem) = '♦'
 get_color(::Gem) = :magenta
@@ -87,6 +92,7 @@ get_color(::Gem) = :magenta
 Base.@kwdef mutable struct Agent <: AbstractObject
     color::Symbol=:red
     dir::LRUD
+    inv::Item=NULL
 end
 function Base.convert(::Type{Char}, a::Agent)
     if        a.dir === UP
@@ -102,3 +108,25 @@ end
 get_color(a::Agent) = a.color
 get_dir(a::Agent) = a.dir
 set_dir!(a::Agent, d) = a.dir = d
+
+#####
+# Pick Up and Drop
+#####
+
+function pickup(a::Agent, o::Item) 
+    if a.Item == NULL 
+        a.Item = o
+        return true
+    end
+    return false
+end
+
+function drop(a::Agent)
+    if a.item != NULL
+        x = a.item
+        a.item = NULL
+        return x
+    end
+    return nothing
+end
+

From cf1963567792326ffa95d82f7b04b62540430bd9 Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Sat, 10 Oct 2020 10:27:49 -0400
Subject: [PATCH 02/28] added pickup() dispatch for non-item objects

---
 src/objects.jl | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/objects.jl b/src/objects.jl
index 03700a5..635ab72 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -120,6 +120,7 @@ function pickup(a::Agent, o::Item)
     end
     return false
 end
+pickup(a::Agent, o::AbstractObject) = nothing
 
 function drop(a::Agent)
     if a.item != NULL

From a55e8a2c6b519d48a175e59ac6f36b9622ff24d9 Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Sat, 10 Oct 2020 10:39:01 -0400
Subject: [PATCH 03/28] changed to use pickup function

---
 src/envs/doorkey.jl | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/envs/doorkey.jl b/src/envs/doorkey.jl
index 16ae961..b61880d 100644
--- a/src/envs/doorkey.jl
+++ b/src/envs/doorkey.jl
@@ -6,7 +6,6 @@ mutable struct DoorKey{W<:GridWorldBase} <: AbstractGridWorld
     world::W
     agent_pos::CartesianIndex{2}
     agent::Agent
-    has_key::Bool
 end
 
 function DoorKey(;n=8, agent_start_pos=CartesianIndex(2,2), rng=Random.GLOBAL_RNG)
@@ -41,13 +40,14 @@ function (w::DoorKey)(::MoveForward)
     dest = dir(w.agent_pos)
 
     if w.world[Key(:yellow), dest]
-        w.has_key = true
-        w.world[Key(:yellow), dest] = false
-        w.world[EMPTY, dest] = true
+        if pickup(w.agent, Key(:yellow))
+            w.world[Key(:yellow), dest] = false
+            w.world[EMPTY, dest] = true
+        end
         w.agent_pos = dest
-    elseif w.world[Door(:yellow), dest] && w.has_key
+    elseif w.world[Door(:yellow), dest] && w.agent.inv == Key(:yellow)
         w.agent_pos = dest
-    elseif w.world[Door(:yellow), dest] && !w.has_key
+    elseif w.world[Door(:yellow), dest] && w.agent.inv == Key(:yellow)
         nothing
     elseif dest ∈ CartesianIndices((size(w.world, 2), size(w.world, 3))) && !w.world[WALL,dest]
         w.agent_pos = dest

From a96646a789d58cf3b5328b104d9c4ee1d6dd8db1 Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Sat, 10 Oct 2020 10:51:49 -0400
Subject: [PATCH 04/28] fixed missed argument change

---
 src/envs/doorkey.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/envs/doorkey.jl b/src/envs/doorkey.jl
index b61880d..d561116 100644
--- a/src/envs/doorkey.jl
+++ b/src/envs/doorkey.jl
@@ -32,7 +32,7 @@ function DoorKey(;n=8, agent_start_pos=CartesianIndex(2,2), rng=Random.GLOBAL_RN
     world[EMPTY, key_pos] = false
     world[Key(:yellow), key_pos] = true
 
-    DoorKey(world, agent_start_pos, Agent(dir=RIGHT),false)
+    DoorKey(world, agent_start_pos, Agent(dir=RIGHT))
 end
 
 function (w::DoorKey)(::MoveForward)

From bdc2a92256895865b63fc13178a37755a58ad4ff Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Sat, 10 Oct 2020 12:18:41 -0400
Subject: [PATCH 05/28] fixed wrong attribute name

---
 src/objects.jl | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/objects.jl b/src/objects.jl
index 635ab72..0a7bd68 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -114,8 +114,8 @@ set_dir!(a::Agent, d) = a.dir = d
 #####
 
 function pickup(a::Agent, o::Item) 
-    if a.Item == NULL 
-        a.Item = o
+    if a.inv == NULL 
+        a.inv = o
         return true
     end
     return false
@@ -123,9 +123,9 @@ end
 pickup(a::Agent, o::AbstractObject) = nothing
 
 function drop(a::Agent)
-    if a.item != NULL
-        x = a.item
-        a.item = NULL
+    if a.inv != NULL
+        x = a.inv
+        a.inv = NULL
         return x
     end
     return nothing

From 4dd1670abc741ce3c881d92657c7e9cdbdb8c3bf Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Sat, 10 Oct 2020 12:42:52 -0400
Subject: [PATCH 06/28] fixed bug allowing passage through door w/o key

---
 src/envs/doorkey.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/envs/doorkey.jl b/src/envs/doorkey.jl
index d561116..9683f6a 100644
--- a/src/envs/doorkey.jl
+++ b/src/envs/doorkey.jl
@@ -47,7 +47,7 @@ function (w::DoorKey)(::MoveForward)
         w.agent_pos = dest
     elseif w.world[Door(:yellow), dest] && w.agent.inv == Key(:yellow)
         w.agent_pos = dest
-    elseif w.world[Door(:yellow), dest] && w.agent.inv == Key(:yellow)
+    elseif w.world[Door(:yellow), dest] && w.agent.inv != Key(:yellow)
         nothing
     elseif dest ∈ CartesianIndices((size(w.world, 2), size(w.world, 3))) && !w.world[WALL,dest]
         w.agent_pos = dest

From 0d6c5a19d9d0ec94f619470496a4c3769e569ba9 Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Sun, 11 Oct 2020 14:53:40 -0400
Subject: [PATCH 07/28] replaced NULL with `nothing`

---
 src/objects.jl | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/src/objects.jl b/src/objects.jl
index 0a7bd68..c3b5306 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -53,10 +53,6 @@ const TURN_LEFT = TurnLeft()
 abstract type AbstractObject end
 abstract type Item <: AbstractObject end
 
-# Placeholder for empty inventory
-struct Null <: Item end
-const NULL = Null()
-
 Base.show(io::IO, x::AbstractObject) = print(io, Crayon(foreground=get_color(x), reset=true), convert(Char, x))
 
 struct Empty <: AbstractObject end
@@ -92,7 +88,7 @@ get_color(::Gem) = :magenta
 Base.@kwdef mutable struct Agent <: AbstractObject
     color::Symbol=:red
     dir::LRUD
-    inv::Item=NULL
+    inv::Union{Item, Nothing}
 end
 function Base.convert(::Type{Char}, a::Agent)
     if        a.dir === UP
@@ -114,7 +110,7 @@ set_dir!(a::Agent, d) = a.dir = d
 #####
 
 function pickup(a::Agent, o::Item) 
-    if a.inv == NULL 
+    if a.inv == nothing
         a.inv = o
         return true
     end
@@ -123,9 +119,9 @@ end
 pickup(a::Agent, o::AbstractObject) = nothing
 
 function drop(a::Agent)
-    if a.inv != NULL
+    if a.inv != nothing
         x = a.inv
-        a.inv = NULL
+        a.inv = nothing
         return x
     end
     return nothing

From 922529c8fbb48e6090ee3f6d3a358a1b1ead5951 Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Mon, 12 Oct 2020 08:32:34 -0400
Subject: [PATCH 08/28] Added trait-based implementation of pickup

---
 src/objects.jl | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/src/objects.jl b/src/objects.jl
index c3b5306..4bb4438 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -51,7 +51,6 @@ const TURN_LEFT = TurnLeft()
 #####
 
 abstract type AbstractObject end
-abstract type Item <: AbstractObject end
 
 Base.show(io::IO, x::AbstractObject) = print(io, Crayon(foreground=get_color(x), reset=true), convert(Char, x))
 
@@ -75,12 +74,12 @@ Door(c) = Door{c}()
 Base.convert(::Type{Char}, ::Door) = '⩎'
 get_color(::Door{C}) where C = C
 
-struct Key{C} <: Item end
+struct Key{C} <: AbstractObject end
 Key(c) = Key{c}()
 Base.convert(::Type{Char}, ::Key) = '⚷'
 get_color(::Key{C}) where C = C
 
-struct Gem <: Item end
+struct Gem <: AbstractObject end
 const GEM = Gem()
 Base.convert(::Type{Char}, ::Gem) = '♦'
 get_color(::Gem) = :magenta
@@ -88,7 +87,7 @@ get_color(::Gem) = :magenta
 Base.@kwdef mutable struct Agent <: AbstractObject
     color::Symbol=:red
     dir::LRUD
-    inv::Union{Item, Nothing}
+    inv::Union{AbstractObject, Nothing}=nothing
 end
 function Base.convert(::Type{Char}, a::Agent)
     if        a.dir === UP
@@ -109,14 +108,23 @@ set_dir!(a::Agent, d) = a.dir = d
 # Pick Up and Drop
 #####
 
-function pickup(a::Agent, o::Item) 
+struct Item end
+struct Nonitem end
+const ITEM = Item()
+const NONITEM = Nonitem()
+isitem(::Type{Key{T}}) where T = ITEM
+isitem(::Type{Gem}) = ITEM
+isitem() = NONITEM
+
+pickup(a::Agent, o::T) where T = pickup(isitem(T), a, o)
+function pickup(::Item, a::Agent, o::AbstractObject) 
     if a.inv == nothing
         a.inv = o
         return true
     end
     return false
 end
-pickup(a::Agent, o::AbstractObject) = nothing
+pickup(a::Agent, ::Nonitem, o::AbstractObject) = nothing
 
 function drop(a::Agent)
     if a.inv != nothing

From 26b536dd695c507ecc780abb9c025dd71c88a776 Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Mon, 12 Oct 2020 08:54:00 -0400
Subject: [PATCH 09/28] Made pickup and drop functors

---
 src/envs/doorkey.jl |  2 +-
 src/objects.jl      | 10 ++++++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/envs/doorkey.jl b/src/envs/doorkey.jl
index 9683f6a..4d6a4e6 100644
--- a/src/envs/doorkey.jl
+++ b/src/envs/doorkey.jl
@@ -40,7 +40,7 @@ function (w::DoorKey)(::MoveForward)
     dest = dir(w.agent_pos)
 
     if w.world[Key(:yellow), dest]
-        if pickup(w.agent, Key(:yellow))
+        if PICKUP(w.agent, Key(:yellow))
             w.world[Key(:yellow), dest] = false
             w.world[EMPTY, dest] = true
         end
diff --git a/src/objects.jl b/src/objects.jl
index 4bb4438..621a074 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -116,7 +116,10 @@ isitem(::Type{Key{T}}) where T = ITEM
 isitem(::Type{Gem}) = ITEM
 isitem() = NONITEM
 
-pickup(a::Agent, o::T) where T = pickup(isitem(T), a, o)
+struct Pickup end
+const PICKUP = Pickup()
+
+(::Pickup)(a::Agent, o::T) where T = pickup(isitem(T), a, o)
 function pickup(::Item, a::Agent, o::AbstractObject) 
     if a.inv == nothing
         a.inv = o
@@ -126,7 +129,10 @@ function pickup(::Item, a::Agent, o::AbstractObject)
 end
 pickup(a::Agent, ::Nonitem, o::AbstractObject) = nothing
 
-function drop(a::Agent)
+struct Drop end
+const DROP = Drop()
+
+function (::Drop)(a::Agent)
     if a.inv != nothing
         x = a.inv
         a.inv = nothing

From 50fb8ca9820656e58779703009d57821c3ba8d45 Mon Sep 17 00:00:00 2001
From: Ben Landrum <36489943+landrumb@users.noreply.github.com>
Date: Mon, 12 Oct 2020 19:29:49 -0400
Subject: [PATCH 10/28] Fix error in train implementation

Co-authored-by: Jun Tian <find_my_way@foxmail.com>
---
 src/objects.jl | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/src/objects.jl b/src/objects.jl
index 621a074..c009b03 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -127,7 +127,7 @@ function pickup(::Item, a::Agent, o::AbstractObject)
     end
     return false
 end
-pickup(a::Agent, ::Nonitem, o::AbstractObject) = nothing
+pickup(::Nonitem, a::Agent, o::AbstractObject) = nothing
 
 struct Drop end
 const DROP = Drop()
@@ -140,4 +140,3 @@ function (::Drop)(a::Agent)
     end
     return nothing
 end
-

From a896252cefab06c5cc1745943832c9cf90c635df Mon Sep 17 00:00:00 2001
From: Ben Landrum <36489943+landrumb@users.noreply.github.com>
Date: Mon, 12 Oct 2020 19:31:40 -0400
Subject: [PATCH 11/28] added type annotation for non-item isitem()

Co-authored-by: Jun Tian <find_my_way@foxmail.com>
---
 src/objects.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/objects.jl b/src/objects.jl
index c009b03..ed61ae3 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -114,7 +114,7 @@ const ITEM = Item()
 const NONITEM = Nonitem()
 isitem(::Type{Key{T}}) where T = ITEM
 isitem(::Type{Gem}) = ITEM
-isitem() = NONITEM
+isitem(x::AbstractObject) = isitem(typeof(x))
 
 struct Pickup end
 const PICKUP = Pickup()

From e511da04748f41436271b7512172bfdb7227eee6 Mon Sep 17 00:00:00 2001
From: Ben Landrum <36489943+landrumb@users.noreply.github.com>
Date: Mon, 12 Oct 2020 19:33:43 -0400
Subject: [PATCH 12/28] made key annotation in isitem trait cleaner

Co-authored-by: Jun Tian <find_my_way@foxmail.com>
---
 src/objects.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/objects.jl b/src/objects.jl
index ed61ae3..0f6a5b3 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -112,7 +112,7 @@ struct Item end
 struct Nonitem end
 const ITEM = Item()
 const NONITEM = Nonitem()
-isitem(::Type{Key{T}}) where T = ITEM
+isitem(::Type{<:Key}) = ITEM
 isitem(::Type{Gem}) = ITEM
 isitem(x::AbstractObject) = isitem(typeof(x))
 

From 849d53719e936aa31a2b531f72326ddb09841c4e Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Tue, 13 Oct 2020 06:05:55 -0400
Subject: [PATCH 13/28] moved drop functor definition to pickup definition

---
 src/objects.jl | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/objects.jl b/src/objects.jl
index 0f6a5b3..0320486 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -119,6 +119,9 @@ isitem(x::AbstractObject) = isitem(typeof(x))
 struct Pickup end
 const PICKUP = Pickup()
 
+struct Drop end
+const DROP = Drop()
+
 (::Pickup)(a::Agent, o::T) where T = pickup(isitem(T), a, o)
 function pickup(::Item, a::Agent, o::AbstractObject) 
     if a.inv == nothing
@@ -129,9 +132,6 @@ function pickup(::Item, a::Agent, o::AbstractObject)
 end
 pickup(::Nonitem, a::Agent, o::AbstractObject) = nothing
 
-struct Drop end
-const DROP = Drop()
-
 function (::Drop)(a::Agent)
     if a.inv != nothing
         x = a.inv

From c9bc6e04e840459c0f1a566d4072233cbb92de21 Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Tue, 13 Oct 2020 06:09:01 -0400
Subject: [PATCH 14/28] refactored item to transportable

---
 src/objects.jl | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/src/objects.jl b/src/objects.jl
index 0320486..aa00dc6 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -108,13 +108,13 @@ set_dir!(a::Agent, d) = a.dir = d
 # Pick Up and Drop
 #####
 
-struct Item end
-struct Nonitem end
-const ITEM = Item()
-const NONITEM = Nonitem()
-isitem(::Type{<:Key}) = ITEM
-isitem(::Type{Gem}) = ITEM
-isitem(x::AbstractObject) = isitem(typeof(x))
+struct Transportable end
+struct Nontransportable end
+const TRANSPORTABLE = Transportable()
+const NONTRANSPORTABLE = Nontransportable()
+istransportable(::Type{<:Key}) = TRANSPORTABLE
+istransportable(::Type{Gem}) = TRANSPORTABLE
+istransportable(x::AbstractObject) = istransportable(typeof(x))
 
 struct Pickup end
 const PICKUP = Pickup()
@@ -122,15 +122,15 @@ const PICKUP = Pickup()
 struct Drop end
 const DROP = Drop()
 
-(::Pickup)(a::Agent, o::T) where T = pickup(isitem(T), a, o)
-function pickup(::Item, a::Agent, o::AbstractObject) 
+(::Pickup)(a::Agent, o::T) where T = pickup(istransportable(T), a, o)
+function pickup(::Transportable, a::Agent, o::AbstractObject) 
     if a.inv == nothing
         a.inv = o
         return true
     end
     return false
 end
-pickup(::Nonitem, a::Agent, o::AbstractObject) = nothing
+pickup(::Nontransportable, a::Agent, o::AbstractObject) = nothing
 
 function (::Drop)(a::Agent)
     if a.inv != nothing

From a774ece30e67afbbe18796952b462d8aa0555f45 Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Tue, 13 Oct 2020 06:30:53 -0400
Subject: [PATCH 15/28] added array_agent

---
 src/objects.jl | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/src/objects.jl b/src/objects.jl
index aa00dc6..0f8bb29 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -84,12 +84,24 @@ const GEM = Gem()
 Base.convert(::Type{Char}, ::Gem) = '♦'
 get_color(::Gem) = :magenta
 
-Base.@kwdef mutable struct Agent <: AbstractObject
+abstract type AbstractAgent <: AbstractObject end
+
+Base.@kwdef mutable struct Agent <: AbstractAgent
     color::Symbol=:red
     dir::LRUD
     inv::Union{AbstractObject, Nothing}=nothing
 end
-function Base.convert(::Type{Char}, a::Agent)
+
+Base.@kwdef mutable struct Array_agent <: AbstractAgent
+    color::Symbol=:red
+    dir::LRUD
+    inv::Vector{Union{AbstractObject, Nothing}}=[]
+end
+function Array_agent(dir::LRUD, len::Integer; color::Symbol=:red)
+    Array_agent(color, dir, Vector{Union{AbstractObject, Nothing}}(nothing, len))
+end
+
+function Base.convert(::Type{Char}, a::AbstractAgent)
     if        a.dir === UP
         '↑'
     elseif  a.dir === DOWN
@@ -100,9 +112,9 @@ function Base.convert(::Type{Char}, a::Agent)
         '→'
     end
 end
-get_color(a::Agent) = a.color
-get_dir(a::Agent) = a.dir
-set_dir!(a::Agent, d) = a.dir = d
+get_color(a::AbstractAgent) = a.color
+get_dir(a::AbstractAgent) = a.dir
+set_dir!(a::AbstractAgent, d) = a.dir = d
 
 #####
 # Pick Up and Drop

From 8fe68296e580a8aba647d21b860759b4f1eab4be Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Tue, 13 Oct 2020 06:53:40 -0400
Subject: [PATCH 16/28] implemented pickup and drop for array_agent

---
 src/objects.jl | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/src/objects.jl b/src/objects.jl
index 0f8bb29..37d9dc7 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -134,15 +134,24 @@ const PICKUP = Pickup()
 struct Drop end
 const DROP = Drop()
 
-(::Pickup)(a::Agent, o::T) where T = pickup(istransportable(T), a, o)
-function pickup(::Transportable, a::Agent, o::AbstractObject) 
+(::Pickup)(a::AbstractAgent, o::T) where T = PICKUP(istransportable(T), a, o)
+function (::Pickup)(::Transportable, a::Agent, o::AbstractObject) 
     if a.inv == nothing
         a.inv = o
         return true
     end
     return false
 end
-pickup(::Nontransportable, a::Agent, o::AbstractObject) = nothing
+function (::Pickup)(::Transportable, a::Array_agent, o::AbstractObject) 
+    for (i, v) in enumerate(a.inv) # Picked up objects go into the first empty index
+        if v == nothing
+            a.inv[i] = o
+            return true
+        end
+    end
+    return false
+end
+pickup(::Nontransportable, a::AbstractAgent, o::AbstractObject) = nothing
 
 function (::Drop)(a::Agent)
     if a.inv != nothing
@@ -152,3 +161,12 @@ function (::Drop)(a::Agent)
     end
     return nothing
 end
+function (::Drop)(a::Array_agent)
+    for (i, v) in Iterators.reverse(enumerate(a.inv)) # Most recently picked up objects are dropped first
+        if typeof(v)<:AbstractObject
+            a.inv[i] = nothing
+            return v
+        end
+    end
+    return nothing
+end

From 1b3efdc87419c71632613662bcababc39832d072 Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Tue, 13 Oct 2020 07:00:58 -0400
Subject: [PATCH 17/28] updated export statements

---
 src/objects.jl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/objects.jl b/src/objects.jl
index 37d9dc7..d23491f 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -1,5 +1,5 @@
-export COLORS, MOVE_FORWARD, TURN_LEFT, TURN_RIGHT, UP, DOWN, LEFT, RIGHT, LRUD, EMPTY, WALL, GOAL, GEM
-export MoveForward, AbstractObject, Empty, Wall, Goal, Door, Gem, Agent
+export COLORS, MOVE_FORWARD, TURN_LEFT, TURN_RIGHT, UP, DOWN, LEFT, RIGHT, LRUD, EMPTY, WALL, GOAL, GEM, PICKUP, DROP
+export MoveForward, AbstractObject, Empty, Wall, Goal, Door, Gem, Agent, Array_agent
 export get_color
 
 using Crayons

From 89759ae53a46cd937606f07ec781b6863d3b1579 Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Tue, 13 Oct 2020 07:09:20 -0400
Subject: [PATCH 18/28] Revert "updated export statements"

This reverts commit 1b3efdc87419c71632613662bcababc39832d072.
---
 src/objects.jl | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/objects.jl b/src/objects.jl
index d23491f..37d9dc7 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -1,5 +1,5 @@
-export COLORS, MOVE_FORWARD, TURN_LEFT, TURN_RIGHT, UP, DOWN, LEFT, RIGHT, LRUD, EMPTY, WALL, GOAL, GEM, PICKUP, DROP
-export MoveForward, AbstractObject, Empty, Wall, Goal, Door, Gem, Agent, Array_agent
+export COLORS, MOVE_FORWARD, TURN_LEFT, TURN_RIGHT, UP, DOWN, LEFT, RIGHT, LRUD, EMPTY, WALL, GOAL, GEM
+export MoveForward, AbstractObject, Empty, Wall, Goal, Door, Gem, Agent
 export get_color
 
 using Crayons

From a8dfb6dc6fc4f07b540b2e4b614e4354dca8acfe Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Tue, 13 Oct 2020 08:46:47 -0400
Subject: [PATCH 19/28] Implemented Agent as a parametric struct

---
 src/objects.jl | 45 ++++++++++++++++++++-------------------------
 1 file changed, 20 insertions(+), 25 deletions(-)

diff --git a/src/objects.jl b/src/objects.jl
index f578270..ad411d0 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -45,26 +45,22 @@ const GEM = Gem()
 Base.convert(::Type{Char}, ::Gem) = '♦'
 get_color(::Gem) = :magenta
 
-abstract type AbstractAgent <: AbstractObject end
+const INV = Union{Nothing, AbstractObject}
+const INVARRAY = Vector{Union{AbstractObject, Nothing}}
 
-Base.@kwdef mutable struct Agent <: AbstractAgent
-    color::Symbol=:red
+mutable struct Agent{I<:Union{INV, INVARRAY}} <: AbstractObject
+    color::Symbol
     dir::LRUD
-    inv::Union{AbstractObject, Nothing}=nothing
+    inv::I
 end
-
-Base.@kwdef mutable struct Array_agent <: AbstractAgent
-    color::Symbol=:red
-    dir::LRUD
-    inv::Vector{Union{AbstractObject, Nothing}}=[]
-end
-
-function Array_agent(dir::LRUD, len::Integer; color::Symbol=:red)
-    Array_agent(color, dir, Vector{Union{AbstractObject, Nothing}}(nothing, len))
+Agent(dir::LRUD; inv::INV=nothing, color::Symbol=:red) = Agent{INV}(color, dir, inv)
+Agent(;dir::LRUD, inv::INV=nothing, color::Symbol=:red) = Agent{INV}(color, dir, inv)
+function Agent{INVARRAY}(dir::LRUD, len::Integer; color::Symbol=:red)
+    Agent{INVARRAY}(color, dir, INVARRAY(nothing, len))
 end
+Agent{INV}(dir::LRUD; inv::INV=nothing, color::Symbol=:red) = Agent{INV}(color, dir, inv)
 
-function Base.convert(::Type{Char}, a::AbstractAgent)
-
+function Base.convert(::Type{Char}, a::Agent)
     if        a.dir === UP
         '↑'
     elseif  a.dir === DOWN
@@ -75,10 +71,9 @@ function Base.convert(::Type{Char}, a::AbstractAgent)
         '→'
     end
 end
-
-get_color(a::AbstractAgent) = a.color
-get_dir(a::AbstractAgent) = a.dir
-set_dir!(a::AbstractAgent, d) = a.dir = d
+get_color(a::Agent) = a.color
+get_dir(a::Agent) = a.dir
+set_dir!(a::Agent, d) = a.dir = d
 
 #####
 # Pick Up and Drop
@@ -98,15 +93,15 @@ const PICKUP = Pickup()
 struct Drop end
 const DROP = Drop()
 
-(::Pickup)(a::AbstractAgent, o::T) where T = PICKUP(istransportable(T), a, o)
-function (::Pickup)(::Transportable, a::Agent, o::AbstractObject) 
+(::Pickup)(a::Agent, o::T) where T = PICKUP(istransportable(T), a, o)
+function (::Pickup)(::Transportable, a::Agent{INV}, o::AbstractObject) 
     if a.inv == nothing
         a.inv = o
         return true
     end
     return false
 end
-function (::Pickup)(::Transportable, a::Array_agent, o::AbstractObject) 
+function (::Pickup)(::Transportable, a::Agent{INVARRAY}, o::AbstractObject) 
     for (i, v) in enumerate(a.inv) # Picked up objects go into the first empty index
         if v == nothing
             a.inv[i] = o
@@ -115,9 +110,9 @@ function (::Pickup)(::Transportable, a::Array_agent, o::AbstractObject)
     end
     return false
 end
-pickup(::Nontransportable, a::AbstractAgent, o::AbstractObject) = nothing
+pickup(::Nontransportable, a::Agent, o::AbstractObject) = nothing
 
-function (::Drop)(a::Agent)
+function (::Drop)(a::Agent{INV})
     if a.inv != nothing
         x = a.inv
         a.inv = nothing
@@ -125,7 +120,7 @@ function (::Drop)(a::Agent)
     end
     return nothing
 end
-function (::Drop)(a::Array_agent)
+function (::Drop)(a::Agent{INVARRAY})
     for (i, v) in Iterators.reverse(enumerate(a.inv)) # Most recently picked up objects are dropped first
         if typeof(v)<:AbstractObject
             a.inv[i] = nothing

From c2daeac389709f989848f1774ae91fbc750af25e Mon Sep 17 00:00:00 2001
From: Jun Tian <tianjun.cpp@gmail.com>
Date: Tue, 13 Oct 2020 22:48:00 +0800
Subject: [PATCH 20/28] slightly polish

---
 src/actions.jl      |  6 +++
 src/envs/doorkey.jl |  8 ++--
 src/objects.jl      | 89 ++++++++++++++++++++-------------------------
 3 files changed, 50 insertions(+), 53 deletions(-)

diff --git a/src/actions.jl b/src/actions.jl
index 33006bd..5f30c21 100644
--- a/src/actions.jl
+++ b/src/actions.jl
@@ -24,3 +24,9 @@ const TURN_LEFT = TurnLeft()
 (x::TurnLeft)(::Up) = LEFT
 (x::TurnLeft)(::Right) = UP
 (x::TurnLeft)(::Down) = RIGHT
+
+struct Pickup <: AbstractGridWorldAction end
+const PICK_UP = Pickup()
+
+struct Drop <: AbstractGridWorldAction end
+const DROP = Drop()
diff --git a/src/envs/doorkey.jl b/src/envs/doorkey.jl
index 4d6a4e6..942d343 100644
--- a/src/envs/doorkey.jl
+++ b/src/envs/doorkey.jl
@@ -32,7 +32,7 @@ function DoorKey(;n=8, agent_start_pos=CartesianIndex(2,2), rng=Random.GLOBAL_RN
     world[EMPTY, key_pos] = false
     world[Key(:yellow), key_pos] = true
 
-    DoorKey(world, agent_start_pos, Agent(dir=RIGHT))
+    DoorKey(world, agent_start_pos, Agent(;dir=RIGHT))
 end
 
 function (w::DoorKey)(::MoveForward)
@@ -45,10 +45,10 @@ function (w::DoorKey)(::MoveForward)
             w.world[EMPTY, dest] = true
         end
         w.agent_pos = dest
-    elseif w.world[Door(:yellow), dest] && w.agent.inv == Key(:yellow)
-        w.agent_pos = dest
-    elseif w.world[Door(:yellow), dest] && w.agent.inv != Key(:yellow)
+    elseif w.world[Door(:yellow), dest] && w.agent.inv !== Key(:yellow)
         nothing
+    elseif w.world[Door(:yellow), dest] && w.agent.inventory === Key(:yellow)
+        w.agent_pos = dest
     elseif dest ∈ CartesianIndices((size(w.world, 2), size(w.world, 3))) && !w.world[WALL,dest]
         w.agent_pos = dest
     end
diff --git a/src/objects.jl b/src/objects.jl
index ad411d0..08fd2fa 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -45,40 +45,34 @@ const GEM = Gem()
 Base.convert(::Type{Char}, ::Gem) = '♦'
 get_color(::Gem) = :magenta
 
-const INV = Union{Nothing, AbstractObject}
-const INVARRAY = Vector{Union{AbstractObject, Nothing}}
+#####
+# Agent
+#####
 
-mutable struct Agent{I<:Union{INV, INVARRAY}} <: AbstractObject
+mutable struct Agent{I<:Union{Nothing, AbstractObject, Vector}} <: AbstractObject
     color::Symbol
     dir::LRUD
-    inv::I
+    inventory::I
 end
-Agent(dir::LRUD; inv::INV=nothing, color::Symbol=:red) = Agent{INV}(color, dir, inv)
-Agent(;dir::LRUD, inv::INV=nothing, color::Symbol=:red) = Agent{INV}(color, dir, inv)
-function Agent{INVARRAY}(dir::LRUD, len::Integer; color::Symbol=:red)
-    Agent{INVARRAY}(color, dir, INVARRAY(nothing, len))
-end
-Agent{INV}(dir::LRUD; inv::INV=nothing, color::Symbol=:red) = Agent{INV}(color, dir, inv)
+
+Agent(;dir::LRUD, inventory=nothing, color::Symbol=:red) = Agent(color, dir, inventory)
 
 function Base.convert(::Type{Char}, a::Agent)
-    if        a.dir === UP
+    if     a.dir === UP
         '↑'
-    elseif  a.dir === DOWN
+    elseif a.dir === DOWN
         '↓'
-    elseif  a.dir === LEFT
+    elseif a.dir === LEFT
         '←'
     elseif a.dir === RIGHT
         '→'
     end
 end
+
 get_color(a::Agent) = a.color
 get_dir(a::Agent) = a.dir
 set_dir!(a::Agent, d) = a.dir = d
 
-#####
-# Pick Up and Drop
-#####
-
 struct Transportable end
 struct Nontransportable end
 const TRANSPORTABLE = Transportable()
@@ -87,45 +81,42 @@ istransportable(::Type{<:Key}) = TRANSPORTABLE
 istransportable(::Type{Gem}) = TRANSPORTABLE
 istransportable(x::AbstractObject) = istransportable(typeof(x))
 
-struct Pickup end
-const PICKUP = Pickup()
-
-struct Drop end
-const DROP = Drop()
-
-(::Pickup)(a::Agent, o::T) where T = PICKUP(istransportable(T), a, o)
-function (::Pickup)(::Transportable, a::Agent{INV}, o::AbstractObject) 
-    if a.inv == nothing
-        a.inv = o
-        return true
-    end
-    return false
-end
-function (::Pickup)(::Transportable, a::Agent{INVARRAY}, o::AbstractObject) 
-    for (i, v) in enumerate(a.inv) # Picked up objects go into the first empty index
-        if v == nothing
-            a.inv[i] = o
-            return true
+(a::Pickup)(a::Agent, o) = a(istransportable(o), a, o)
+
+function (::Pickup)(::Transportable, a::Agent, o::AbstractObject) 
+    if isnothing(a.inventory)
+        a.inventory = o
+        true
+    elseif a.inventory isa Vector
+        i = findfirst(isnothing, a.v)
+        if isnothing(i)
+            false
+        else
+            a.inventory[i] = o
+            true
         end
+    else
+        false
     end
-    return false
 end
-pickup(::Nontransportable, a::Agent, o::AbstractObject) = nothing
 
-function (::Drop)(a::Agent{INV})
-    if a.inv != nothing
+function (::Drop)(a::Agent)
+    if isnothing(a.inv)
+        nothing
+    elseif a.inv isa AbstractObject
         x = a.inv
         a.inv = nothing
-        return x
-    end
-    return nothing
-end
-function (::Drop)(a::Agent{INVARRAY})
-    for (i, v) in Iterators.reverse(enumerate(a.inv)) # Most recently picked up objects are dropped first
-        if typeof(v)<:AbstractObject
+        x
+    elseif a.inv isa Vector
+        i = findlast(x -> x isa AbstractObject, a.inv)
+        if isnothing(i)
+            nothing
+        else
+            x = a.inv[i]
             a.inv[i] = nothing
-            return v
+            x
         end
+    else
+        @error "unknown inventory type $(a.inv)"
     end
-    return nothing
 end

From 9c11a9c6d03adb97f2f1c27936f4a949db224024 Mon Sep 17 00:00:00 2001
From: Jun Tian <juti@microsoft.com>
Date: Tue, 13 Oct 2020 23:17:34 +0800
Subject: [PATCH 21/28] fix DoorKey

---
 src/envs/doorkey.jl |  4 ++--
 src/objects.jl      | 24 ++++++++++++------------
 2 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/src/envs/doorkey.jl b/src/envs/doorkey.jl
index 942d343..703a268 100644
--- a/src/envs/doorkey.jl
+++ b/src/envs/doorkey.jl
@@ -40,12 +40,12 @@ function (w::DoorKey)(::MoveForward)
     dest = dir(w.agent_pos)
 
     if w.world[Key(:yellow), dest]
-        if PICKUP(w.agent, Key(:yellow))
+        if PICK_UP(w.agent, Key(:yellow))
             w.world[Key(:yellow), dest] = false
             w.world[EMPTY, dest] = true
         end
         w.agent_pos = dest
-    elseif w.world[Door(:yellow), dest] && w.agent.inv !== Key(:yellow)
+    elseif w.world[Door(:yellow), dest] && w.agent.inventory !== Key(:yellow)
         nothing
     elseif w.world[Door(:yellow), dest] && w.agent.inventory === Key(:yellow)
         w.agent_pos = dest
diff --git a/src/objects.jl b/src/objects.jl
index 08fd2fa..af58568 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -49,10 +49,10 @@ get_color(::Gem) = :magenta
 # Agent
 #####
 
-mutable struct Agent{I<:Union{Nothing, AbstractObject, Vector}} <: AbstractObject
+mutable struct Agent <: AbstractObject
     color::Symbol
     dir::LRUD
-    inventory::I
+    inventory::Union{Nothing, AbstractObject, Vector}
 end
 
 Agent(;dir::LRUD, inventory=nothing, color::Symbol=:red) = Agent(color, dir, inventory)
@@ -81,7 +81,7 @@ istransportable(::Type{<:Key}) = TRANSPORTABLE
 istransportable(::Type{Gem}) = TRANSPORTABLE
 istransportable(x::AbstractObject) = istransportable(typeof(x))
 
-(a::Pickup)(a::Agent, o) = a(istransportable(o), a, o)
+(x::Pickup)(a::Agent, o) = x(istransportable(o), a, o)
 
 function (::Pickup)(::Transportable, a::Agent, o::AbstractObject) 
     if isnothing(a.inventory)
@@ -101,22 +101,22 @@ function (::Pickup)(::Transportable, a::Agent, o::AbstractObject)
 end
 
 function (::Drop)(a::Agent)
-    if isnothing(a.inv)
+    if isnothing(a.inventory)
         nothing
-    elseif a.inv isa AbstractObject
-        x = a.inv
-        a.inv = nothing
+    elseif a.inventory isa AbstractObject
+        x = a.inventory
+        a.inventory = nothing
         x
-    elseif a.inv isa Vector
-        i = findlast(x -> x isa AbstractObject, a.inv)
+    elseif a.inventory isa Vector
+        i = findlast(x -> x isa AbstractObject, a.inventory)
         if isnothing(i)
             nothing
         else
-            x = a.inv[i]
-            a.inv[i] = nothing
+            x = a.inventory[i]
+            a.inventory[i] = nothing
             x
         end
     else
-        @error "unknown inventory type $(a.inv)"
+        @error "unknown inventory type $(a.inventory)"
     end
 end

From 891e588578463c0e7fe6a506f66064268a92dbce Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Fri, 16 Oct 2020 13:48:35 -0400
Subject: [PATCH 22/28] Added backend for perspective occlusion

---
 src/grid_world_base.jl | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)

diff --git a/src/grid_world_base.jl b/src/grid_world_base.jl
index cf3fb14..73e9060 100644
--- a/src/grid_world_base.jl
+++ b/src/grid_world_base.jl
@@ -60,6 +60,41 @@ function Random.rand(f::Function, w::GridWorldBase; max_try=typemax(Int), rng=Ra
     return nothing
 end
 
+#####
+# Occlusion
+#####
+
+radius(x, y) = √(x^2 + y^2)
+radius(p::Tuple) = radius(p[1], p[2])
+theta(x, y) = x == 0 ? sign(y)*π/2 : atan(y, x)
+theta(p::Tuple{<:Real}) = theta(p[1], p[2])
+
+struct PolarCoord
+    θ::AbstractFloat
+    r::AbstractFloat
+end
+PolarCoord(θ::AbstractFLoat, r::AbstractFLoat) = PolarCoord((θ + (r<0 && π)) % 2π, abs(r))
+PolarCoord(p::Tuple) = PolarCoord(theta(p), radius(p))
+PolarCoord(p::CartesianIndex) = PolarCoord(Tuple(p))
+
+struct Shadow
+    minθ::AbstractFloat
+    maxθ::AbstractFloat
+    r::AbstractFloat
+end
+function Shadow(p::CartesianIndex)
+    r = radius(Tuple(p))
+    corners = [(p[1]+x, p[2]+y) for x in -.5:.5, y in -.5:.5]
+    corners = theta.(corners)
+    Shadow(min(corners), max(corners), r)
+end
+
+function (s::Shadow)(v::CartesianIndices)
+    polar = PolarCoord.(v)
+    f(x) = x.r > s.r && s.minθ < x.θ <= s.maxθ
+    f.(polar)
+end
+
 #####
 # get_agent_view
 #####

From 8f47a525ddba1504a0cf5e33f325c51fb21a2caa Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Fri, 16 Oct 2020 13:52:52 -0400
Subject: [PATCH 23/28] added light docstring for shadow functor

---
 src/grid_world_base.jl | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/grid_world_base.jl b/src/grid_world_base.jl
index 73e9060..5d6f129 100644
--- a/src/grid_world_base.jl
+++ b/src/grid_world_base.jl
@@ -89,6 +89,10 @@ function Shadow(p::CartesianIndex)
     Shadow(min(corners), max(corners), r)
 end
 
+"""
+returns a 2D array of boolean values, where `true` represents an index which is
+occluded by the shadow `s` evaluating `v`
+"""
 function (s::Shadow)(v::CartesianIndices)
     polar = PolarCoord.(v)
     f(x) = x.r > s.r && s.minθ < x.θ <= s.maxθ

From 08e48fa6ed8e912eacc8874d1ad30159ae3b0493 Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Fri, 16 Oct 2020 19:03:56 -0400
Subject: [PATCH 24/28] Added very light test

---
 src/grid_world_base.jl |  9 +++++----
 test/runtests.jl       | 17 +++++++++++++++++
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/src/grid_world_base.jl b/src/grid_world_base.jl
index 5d6f129..e0e447e 100644
--- a/src/grid_world_base.jl
+++ b/src/grid_world_base.jl
@@ -67,13 +67,13 @@ end
 radius(x, y) = √(x^2 + y^2)
 radius(p::Tuple) = radius(p[1], p[2])
 theta(x, y) = x == 0 ? sign(y)*π/2 : atan(y, x)
-theta(p::Tuple{<:Real}) = theta(p[1], p[2])
+theta(p::Tuple) = theta(p[1], p[2])
 
 struct PolarCoord
     θ::AbstractFloat
     r::AbstractFloat
 end
-PolarCoord(θ::AbstractFLoat, r::AbstractFLoat) = PolarCoord((θ + (r<0 && π)) % 2π, abs(r))
+PolarCoord(θ::Real, r::Real) = PolarCoord((θ + (r<0 && π)) % 2π, abs(r))
 PolarCoord(p::Tuple) = PolarCoord(theta(p), radius(p))
 PolarCoord(p::CartesianIndex) = PolarCoord(Tuple(p))
 
@@ -86,7 +86,7 @@ function Shadow(p::CartesianIndex)
     r = radius(Tuple(p))
     corners = [(p[1]+x, p[2]+y) for x in -.5:.5, y in -.5:.5]
     corners = theta.(corners)
-    Shadow(min(corners), max(corners), r)
+    Shadow(minimum(corners), maximum(corners), r)
 end
 
 """
@@ -95,7 +95,7 @@ occluded by the shadow `s` evaluating `v`
 """
 function (s::Shadow)(v::CartesianIndices)
     polar = PolarCoord.(v)
-    f(x) = x.r > s.r && s.minθ < x.θ <= s.maxθ
+    f(x) = x.r > s.r && s.minθ <= x.θ <= s.maxθ
     f.(polar)
 end
 
@@ -123,5 +123,6 @@ function get_agent_view!(v::AbstractArray{Bool,3}, a::AbstractArray{Bool,3}, p::
             v[:, ind_map(ind.I, view_size, dir)...] .= a[:, inds[ind]]
         end
     end
+
     v
 end
diff --git a/test/runtests.jl b/test/runtests.jl
index 8a28222..64dbf1f 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -28,4 +28,21 @@ ACTIONS = [TURN_LEFT, TURN_RIGHT, MOVE_FORWARD]
             end
         end
     end
+    @testset "grid_world_base.jl" begin
+        grid = CartesianIndices((-3:3, 0:6))
+        soln = 
+        [[1,1,1,1,1,1,1]
+         [1,1,1,1,1,1,1]
+         [1,1,1,1,1,1,1]
+         [1,1,1,1,1,1,1]
+         [1,1,1,1,0,0,1]
+         [0,0,1,1,0,0,1]
+         [0,1,1,1,0,0,0]]
+         
+        s = GridWorlds.Shadow(CartesianIndex((1,3)))
+        println("minθ:$(s.minθ)|maxθ:$(s.maxθ)|r:$(s.r)")
+        println(s(grid))
+        println("($(GridWorlds.theta(3,4)), $(GridWorlds.radius(3,4)))")
+        println(s(CartesianIndices((3:3, 5:5))))
+    end
 end

From 501bca030bae619d58c38ec18cffc6bea85ec1ce Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Sun, 18 Oct 2020 18:14:04 -0400
Subject: [PATCH 25/28] Implemented opacity trait

---
 src/grid_world_base.jl |  2 +-
 src/objects.jl         | 16 ++++++++++++++--
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/grid_world_base.jl b/src/grid_world_base.jl
index e0e447e..dab7b43 100644
--- a/src/grid_world_base.jl
+++ b/src/grid_world_base.jl
@@ -94,7 +94,7 @@ returns a 2D array of boolean values, where `true` represents an index which is
 occluded by the shadow `s` evaluating `v`
 """
 function (s::Shadow)(v::CartesianIndices)
-    polar = PolarCoord.(v)
+    polar = PolarCoord.(v)``
     f(x) = x.r > s.r && s.minθ <= x.θ <= s.maxθ
     f.(polar)
 end
diff --git a/src/objects.jl b/src/objects.jl
index 1fb947e..5d21b2d 100644
--- a/src/objects.jl
+++ b/src/objects.jl
@@ -30,8 +30,10 @@ const GOAL = Goal()
 Base.convert(::Type{Char}, ::Goal) = '♥'
 get_color(::Goal) = :red
 
-struct Door{C} <: AbstractObject end
-Door(c) = Door{c}()
+struct Door{C} <: AbstractObject
+    open::Bool
+end
+Door(c) = Door{c}(false)
 Base.convert(::Type{Char}, ::Door) = '⩎'
 get_color(::Door{C}) where C = C
 
@@ -84,6 +86,16 @@ istransportable(::Type{<:Key}) = TRANSPORTABLE
 istransportable(::Type{Gem}) = TRANSPORTABLE
 istransportable(x::AbstractObject) = istransportable(typeof(x))
 
+struct Opaque end
+struct Transparent end
+const OPAQUE = Opaque()
+const TRANSPARENT = Transparent()
+isopaque(::Type{<:AbstractObject}) = OPAQUE
+isopaque(::Type{<:Key}) = TRANSPARENT
+isopaque(::Type{Gem}) = TRANSPARENT
+isopaque(x::AbstractObject) = isopaque(typeof(x))
+isopaque(x<:Door) = x.open ? TRANSPARENT : OPAQUE
+
 (x::Pickup)(a::Agent, o) = x(istransportable(o), a, o)
 
 function (::Pickup)(::Transportable, a::Agent, o::AbstractObject) 

From a4292af96bb151dc576a81213ab4243efaa9bbd4 Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Mon, 19 Oct 2020 11:55:09 -0400
Subject: [PATCH 26/28] added light docstring for get_agent_view!()

---
 src/grid_world_base.jl | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/src/grid_world_base.jl b/src/grid_world_base.jl
index dab7b43..9b3a9d1 100644
--- a/src/grid_world_base.jl
+++ b/src/grid_world_base.jl
@@ -113,6 +113,15 @@ ind_map((i,j), (m, n), ::Right) = (j, n-i+1)
 ind_map((i,j), (m, n), ::Up) = (m-i+1, n-j+1)
 ind_map((i,j), (m, n), ::Down) = (i,j)
 
+"""
+Updates the agent view
+
+Args:
+    v::AbstractArray{Bool,3}: the current agent view as a 3D array with indices [type, x, y]
+    a::AbstractArray{Bool,3}: the current environment as a 3D array with indices [type, x, y]
+    p::CartesianIndex: location of the agent
+    dir::LRUD: direction the agent is looking
+"""
 function get_agent_view!(v::AbstractArray{Bool,3}, a::AbstractArray{Bool,3}, p::CartesianIndex, dir::LRUD)
     view_size = (size(v, 2), size(v, 3))
     grid_size = (size(a,2),size(a,3))

From f2f5c11a7c4c849126533894ebeec72a49182d7e Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Mon, 19 Oct 2020 14:37:29 -0400
Subject: [PATCH 27/28] Added w to arguments of get_agent_view and simplified

---
 src/abstract_grid_world.jl |  2 --
 src/grid_world_base.jl     | 23 ++++++++++++++++-------
 2 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/src/abstract_grid_world.jl b/src/abstract_grid_world.jl
index e022817..fe4d365 100644
--- a/src/abstract_grid_world.jl
+++ b/src/abstract_grid_world.jl
@@ -32,5 +32,3 @@ get_actions(w::AbstractGridWorld) = (MOVE_FORWARD, TURN_LEFT, TURN_RIGHT)
 
 get_agent_view_inds(w::AbstractGridWorld, s=(7,7)) = get_agent_view_inds(get_agent_pos(w).I, s, get_agent_dir(w))
 
-get_agent_view!(v::BitArray{3}, w::AbstractGridWorld) = get_agent_view!(v, convert(GridWorldBase, w), get_agent_pos(w), get_agent_dir(w))
-
diff --git a/src/grid_world_base.jl b/src/grid_world_base.jl
index 9b3a9d1..3159181 100644
--- a/src/grid_world_base.jl
+++ b/src/grid_world_base.jl
@@ -122,16 +122,25 @@ Args:
     p::CartesianIndex: location of the agent
     dir::LRUD: direction the agent is looking
 """
-function get_agent_view!(v::AbstractArray{Bool,3}, a::AbstractArray{Bool,3}, p::CartesianIndex, dir::LRUD)
+function get_agent_view!(v::AbstractArray{Bool,3}, w::AbstractGridWorld; perspective::Bool=true)
+    a = convert(GridWorldBase, w)
+    p = get_agent_pos(w)
+    dir = get_agent_dir(w)
+
     view_size = (size(v, 2), size(v, 3))
     grid_size = (size(a,2),size(a,3))
-    inds = get_agent_view_inds(p.I, view_size, dir)
-    valid_inds = CartesianIndices(grid_size)
-    for ind in CartesianIndices(inds)
-        if inds[ind] ∈ valid_inds
-            v[:, ind_map(ind.I, view_size, dir)...] .= a[:, inds[ind]]
+    inds = get_agent_view_inds(p.I, view_size, dir) # indices of the visible points
+    valid_inds = CartesianIndices(grid_size) # CartesianIndices representing the whole environment
+
+    if perspective
+        
+    else
+        for ind in CartesianIndices(inds) # for every index in view...
+            if inds[ind] ∈ valid_inds # if it's within the environment...
+                # set its corresponding value in the view to the value in the environment
+                v[:, ind_map(ind.I, view_size, dir)...] .= a[:, inds[ind]]
+            end
         end
     end
-
     v
 end

From e71ea87c6868dec6ab4df09a056576904d226382 Mon Sep 17 00:00:00 2001
From: landrumb <36489943+landrumb@users.noreply.github.com>
Date: Mon, 19 Oct 2020 16:22:08 -0400
Subject: [PATCH 28/28] implemented occlusion to get_agent_view

---
 src/grid_world_base.jl | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/src/grid_world_base.jl b/src/grid_world_base.jl
index 3159181..0bab9a2 100644
--- a/src/grid_world_base.jl
+++ b/src/grid_world_base.jl
@@ -99,6 +99,15 @@ function (s::Shadow)(v::CartesianIndices)
     f.(polar)
 end
 
+function shadowmap(m::Matrix{Bool})
+    indices = CartesianIndices(((-1*size(m)[1]÷2):(size(m)[1]÷2), 0:(size(m)[2]-1)))
+    shadows = Shadow.(indices[m])
+    output = fill(false, size(a))
+    for s in shadows
+        output |= s(indices)
+    end
+    output
+end
 #####
 # get_agent_view
 #####
@@ -133,7 +142,20 @@ function get_agent_view!(v::AbstractArray{Bool,3}, w::AbstractGridWorld; perspec
     valid_inds = CartesianIndices(grid_size) # CartesianIndices representing the whole environment
 
     if perspective
-        
+        m = convert(Matrix{Bool}, copy(v))
+        shadows = []
+        for ind in CartesianIndices(inds) # for every index in view...
+            if inds[ind] ∈ valid_inds # if it's within the environment...
+                o = findfirst(w[:, inds[ind]]) # first object at the index
+                m[ind_map(ind.I, view_size, dir)...] .= isnothing(o) ? false : isopaque(w.objects[o]) <: Opaque
+            end
+        end
+        shadows = .!(shadowmap(m))
+        for ind in CartesianIndices(inds)
+            if inds[ind] ∈ valid_inds && shadows[ind_map(ind.I, view_size, dir)...]
+                v[:, ind_map(ind.I, view_size, dir)...] .= a[:, inds[ind]]
+            end
+        end
     else
         for ind in CartesianIndices(inds) # for every index in view...
             if inds[ind] ∈ valid_inds # if it's within the environment...