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CS 511: Homework Assignment 3

2 Assignment
The aim of this assignment is to get familiar with the functional fragment of Erlang1 and
to learn how to work with some of the data structures provided by the language; notably
lists, maps, and records.
You are asked to implement various operations that provide support to a shipping company.
The shipping company administers (cargo) ships. Ships transport containers and navigate
from one port to another. Each port has a number of docks where the ships may load and
unload. Containers can either be in transit on a ship or in a port (in the latter case, no
distinction is made regarding the specific dock).

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CS 511: Homework Assignment 3

2 Assignment
The aim of this assignment is to get familiar with the functional fragment of Erlang1 and
to learn how to work with some of the data structures provided by the language; notably
lists, maps, and records.
You are asked to implement various operations that provide support to a shipping company.
The shipping company administers (cargo) ships. Ships transport containers and navigate
from one port to another. Each port has a number of docks where the ships may load and
unload. Containers can either be in transit on a ship or in a port (in the latter case, no
distinction is made regarding the specific dock).
You are supplied with two files:
• shipping.hrl. The Erlang header file for the assignment. It contains all the
record declarations you should need to complete this assignment. These are described
in further detail below.
1Disregarding process spawning and message passing. The latter will be addressed in an upcoming
assignment.
1
• shipping.erl. The module file that includes all the functions that need to be
completed. This is the file you will be editing.
2.0.1 Shipping Header File (shipping.hrl)
• Ship This record contains the fields:
· name a string value
· id a unique integer value
· container cap the maximum number of containers that a ship can hold
• Container This record contains the fields:
· id a unique integer value
· weight any positive integer value
• Port This record contains the fields:
· name a string value
· id a unique integer value
· docks a list of docks for the port. A dock can be represented by an unique integer
or a character and is only required to be unique at a given port (i.e. Port ”New
York”, Dock ’A’ and Port ”Los Angeles”, Dock ’A’ are both valid)
· container cap the maximum number of containers that a ship can hold
• Shipping State This record contains the fields:
· ships a list of the ship records currently in the system
· containers a list of the container records currently in the system
· ports a list of the port records currently in the system
· ship locations a tuple containing a port id, dock id, and ship id (i.e.
(1,’A’,3)) if port 1, dock ’A’ contains ship 3
· ship inventory a map that takes a ship id and maps it to the list of containers ids on that ship.
· port inventory a map that takes a port id and maps it to the list of containers ids at that port.
2
3 Shipping Module
We next describe each of the functions you are asked to implement. All of them have to be
defined in shipping.erl.
To illustrate some of the functions described below we will use a sample shipping company
ShipCo. The shipping state of ShipCo may be obtained by calling shipping:shipco().
It is provided for you in the stub. Before you try out the examples below, remember to
compile and then load the record definitions into the interpreter, as follows:
1 c(shipping).
shipping.erl:2: Warning: export_all flag enabled – all functions will be exported
{ok,shipping}
2 rr(shipping).
[container,port,ship,shipping_state]
1. get ship(Shipping State, Ship ID)
This method returns a ship record for the given id. For example,
shipping:get_ship(shipping:shipco(),1) will return the ship whose id is 1. If the
ship does not exist, it returns the atom error.
3 shipping:get_ship(shipping:shipco(),1).
#ship{id = 1,name = “Santa Maria”,container_cap = 20}
4 shipping:get_ship(shipping:shipco(),7).
error
2. get container(Shipping State, Container ID)
This method returns a container record for the given id. It returns the atom error if
the container id does not exist. For example:
5 shipping:get_container(shipping:shipco(),4).
#container{id = 4,weight = 62}
6 shipping:get_container(shipping:shipco(),47).
error
3. get port(Shipping State, Port ID)
This method returns a port records for the given id. It returns the atom error if the
port id does not exist. For example:
7 shipping:get_port(shipping:shipco(),3).
#port{id = 3,name = “Miami”,
docks = [’A’,’B’,’C’,’D’],
container_cap = 200}
8 shipping:get_port(shipping:shipco(),12).
error
4. get occupied docks(Shipping State, Port ID)
This method returns a list of all the occupied docks for a given port. It returns the
empty list if the port id does not exist. For example:
3
9 shipping:get_occupied_docks(shipping:shipco(),3).
[’C’]
10 shipping:get_occupied_docks(shipping:shipco(),23).
[]
5. get ship location(Shipping State, Ship ID)
This method returns the location, {Port ID, Dock ID}, of a given ship. It returns
the atom error if the ship id does not exist. For example:
11 shipping:get_ship_location(shipping:shipco(),3).
{1,’A’}
12 shipping:get_ship_location(shipping:shipco(),23).
error
6. get container weight(Shipping State, Container IDs)
This method returns the total weight of all of the container ids in the list Container IDs.
It returns the atom error if any of the container Ids does not exist.
13 shipping:get_container_weight(shipping:shipco(),[3,5]).
243
14 shipping:get_container_weight(shipping:shipco(),[89,3,5]).
error
7. get ship weight(Shipping State, Ship ID)
This method returns the total weight of a ship, measured by the total weight of the
ship’s containers. It returns the atom error if ship Id does not exist.
15 shipping:get_ship_weight(shipping:shipco(),2).
676
16 shipping:get_ship_weight(shipping:shipco(),22).
error
8. load ship(Shipping State, Ship ID, Container IDs)
This method returns a shipping state in which the containers in the list of Container IDs
are moved from a port to the ship with the given Ship ID. Make sure that all the
containers are at the same port as the ship they are loading onto. In the case that
loading the ship would put the ship over capacity, return an atom error and do not
add any containers to the ship. Here is an example. Notice how containers 16, 18 and
20 have been removed from dock 1 and loaded onto ship 1.
10 shipping:load_ship(shipping:shipco(), 1, [16,18,20]).
{ok,#shipping_state{
ships = [#ship{id = 1,name = “Santa Maria”,container_cap = 20},
#ship{id = 2,name = “Nina”,container_cap = 20},
#ship{id = 3,name = “Pinta”,container_cap = 20},
#ship{id = 4,name = “SS Minnow”, container_cap = 20},
#ship{id = 5,name = “Sir Leaks-A-Lot”,container_cap = 20}],
4
containers = […], %% not shown
ports = [#port{id = 1,name = “New York”,
docks = [’A’,’B’,’C’,’D’],
container_cap = 200},
#port{id = 2,name = “San Francisco”,
docks = [’A’,’B’,’C’,’D’],
container_cap = 200},
#port{id = 3,name = “Miami”,
docks = [’A’,’B’,’C’,’D’],
container_cap = 200}],
ship_locations = [{1,’B’,1},
{1,’A’,3},
{3,’C’,2},
{2,’D’,4},
{2,’B’,5}],
ship_inventory = #{1 = [14,15,9,2,6,16,18,20], %% loaded here
2 = [1,3,4,13],
3 = [],
4 = [2,8,11,7],
5 = [5,10,12]},
port_inventory = #{1 = [17,19], %% removed from port 1
2 = [21,22,23,24,25],
3 = [26,27,28,29,30]}}}
9. unload ship all(Shipping State, Ship ID)
This method returns a shipping state in which all of the containers that are on a given
ship are offloaded to the port in which the ship is docked. In the case that offloading
to a port would put the port over capacity, return an error and do not unload any
containers to the port.
11 shipping:unload_ship_all(shipping:shipco(), 2).
{ok,#shipping_state{
ships = [#ship{id = 1,name = “Santa Maria”,container_cap = 20},
#ship{id = 2,name = “Nina”,container_cap = 20},
#ship{id = 3,name = “Pinta”,container_cap = 20},
#ship{id = 4,name = “SS Minnow”,container_cap = 20},
#ship{id = 5,name = “Sir Leaks-A-Lot”,container_cap = 20}],
containers = […], %% not shown
ports = [#port{id = 1,name = “New York”,
docks = [’A’,’B’,’C’,’D’],
container_cap = 200},
#port{id = 2,name = “San Francisco”,
docks = [’A’,’B’,’C’,’D’],
container_cap = 200},
#port{id = 3,name = “Miami”,
docks = [’A’,’B’,’C’,’D’],
container_cap = 200}],
ship_locations = [{1,’B’,1},
{1,’A’,3},
5
{3,’C’,2},
{2,’D’,4},
{2,’B’,5}],
ship_inventory = #{1 = [14,15,9,2,6],
2 = [], %% no more containers
3 = [],
4 = [2,8,11,7],
5 = [5,10,12]},
port_inventory = #{1 = [16,17,18,19,20],
2 = [21,22,23,24,25],
3 = [26,27,28,29,30,1,3,4,13]} %% loaded here
}}
10. unload ship(Shipping State, Ship ID, Container IDs)
This method returns a shipping state in which the given containers on a ship are
offloaded to the port in which the ship is docked. Make sure that all the containers
are located on the ship. In the case that offloading to a port would put the port over
capacity, return an error and do not offload any containers to the port.
12 shipping:unload_ship(shipping:shipco(), 1, [2,16,18]).
The given conatiners are not all on the same ship…
error
13 shipping:unload_ship(shipping:shipco(), 1, [14,2]).
{ok,#shipping_state{
ships = [#ship{id = 1,name = “Santa Maria”,container_cap = 20},
#ship{id = 2,name = “Nina”,container_cap = 20},
#ship{id = 3,name = “Pinta”,container_cap = 20},
#ship{id = 4,name = “SS Minnow”,container_cap = 20},
#ship{id = 5,name = “Sir Leaks-A-Lot”,container_cap = 20}],
containers = […], %% not shown
ports = [#port{id = 1,name = “New York”,
docks = [’A’,’B’,’C’,’D’],
container_cap = 200},
#port{id = 2,name = “San Francisco”,
docks = [’A’,’B’,’C’,’D’],
container_cap = 200},
#port{id = 3,name = “Miami”,
docks = [’A’,’B’,’C’,’D’],
container_cap = 200}],
ship_locations = [{1,’B’,1},
{1,’A’,3},
{3,’C’,2},
{2,’D’,4},
{2,’B’,5}],
ship_inventory = #{1 = [15,9,6], %% removed from here
2 = [1,3,4,13],
3 = [],
4 = [2,8,11,7],
6
5 = [5,10,12]},
port_inventory = #{1 = [16,17,18,19,20,14,2], %% placed here
2 = [21,22,23,24,25],
3 = [26,27,28,29,30]}}}
11. set sail(Shipping State, Ship ID, {Port ID, Dock})
This method changes the given ship’s port and dock location to the new port and
dock location. Be sure to check whether or not the new port and dock is occupied. If
it is, then return the atom error.
14 shipping:set_sail(shipping:shipco(), 4, {2,’B’}).
error
15 shipping:set_sail(shipping:shipco(), 4, {3,’A’}).
{ok,#shipping_state{
ships = [#ship{id = 1,name = “Santa Maria”,container_cap = 20},
#ship{id = 2,name = “Nina”,container_cap = 20},
#ship{id = 3,name = “Pinta”,container_cap = 20},
#ship{id = 4,name = “SS Minnow”,container_cap = 20},
#ship{id = 5,name = “Sir Leaks-A-Lot”,container_cap = 20}],
containers = […], %% not shown
ports = [#port{id = 1,name = “New York”,
docks = [’A’,’B’,’C’,’D’],
container_cap = 200},
#port{id = 2,name = “San Francisco”,
docks = [’A’,’B’,’C’,’D’],
container_cap = 200},
#port{id = 3,name = “Miami”,
docks = [’A’,’B’,’C’,’D’],
container_cap = 200}],
ship_locations = [{1,’B’,1},
{1,’A’,3},
{3,’C’,2},
{3,’A’,4}, %% new port and dock
{2,’B’,5}],
ship_inventory = #{1 = [14,15,9,2,6],
2 = [1,3,4,13],
3 = [],
4 = [2,8,11,7],
5 = [5,10,12]},
port_inventory = #{1 = [16,17,18,19,20],
2 = [21,22,23,24,25],
3 = [26,27,28,29,30]}}}
4 Your Task
Your task is to complete all the functions in shipping.erl as mentioned above. You DO
NOT have to touch shipping.hrl. Some example modules to help you complete some
7
of these functions would be the lists and maps modules.
5 Submission Instructions
Submit a file hw3.zip through Canvas containing all the files included in the stub but
where all required operations have been implemented. Place the name of both members of
the team both in source code.
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