CS 511: Homework Assignment 3

•

• 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.

◦ shipping.erl. The module file that includes all the functions that need to be completed. This is the file you will be editing.

1Disregarding process spawning and message passing. The latter will be addressed in an upcoming assignment.

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 port 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 contain-ers ids on that ship.

◦ port inventory a map that takes a port id and maps it to the list of con-tainers ids at that port.

• 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:

2

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 should throw the exception error2.

3> shipping:get_ship(shipping:shipco(),1).

#ship{id = 1,name = "Santa Maria",container_cap = 20} 4> shipping:get_ship(shipping:shipco(),7).

◦ exception throw: error

in function shipping:get_ship/2 ...

2. get container(Shipping State, Container ID)

This method returns a container record for the given id. It should throw the exception 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).

◦ exception throw: error

in function shipping:get_container/2 ...

3. get port(Shipping State, Port ID)

This method returns a port records for the given id. It should throw the exception 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).

◦ exception throw: error

in function shipping:get_port/2 ...

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:

9> shipping:get_occupied_docks(shipping:shipco(),3).

[’C’]

10> shipping:get_occupied_docks(shipping:shipco(),23).

[]

• Use throw(my_exception) to throw an exception called my_exception.

3

5. get ship location(Shipping State, Ship ID)

This method returns the location, {Port ID, Dock ID}, of a given ship. It should throw the exception 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).

◦ exception throw: error

in function shipping:get_ship_location/2 ...

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 should throw the exception 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]).

** exception throw: error

in function shipping:get_container/2 ...

...

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).

** exception throw: error

in function shipping:get_ship_weight/2

8. load ship(Shipping State, Ship ID, Container IDs)

This method returns a shipping state in which the containers in the list Container IDs are moved from a port to the ship with the given Ship ID. Assume Container IDs has no duplicates. You must, however, make sure that all the containers are at the same port as the ship they are loading onto. In the case that Ship ID does not exist or that the loading the ship would put the ship over capacity, throw an error exception and do not add any containers to the ship. Also throw an error exception if there are container IDs that aren’t in the same port as the ship or if the containers are already on 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},

4

#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 => [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]}}}

> shipping:load_ship(shipping:shipco(), 45, [16,18,20]). ** exception throw: error

in function shipping:get_ship/2 ...

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, throw the exception error atom 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},

5

#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],

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, throw the exception error and do not offload any containers to the port. Also throw the exception error if the container ID is not on the ship.

12> shipping:unload_ship(shipping:shipco(), 1, [2,16,18]).

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},

6

{2,’B’,5}],

ship_inventory = #{1

=> [15,9,6], %% removed from here

2

=> [1,3,4,13],

3

=> [],

4

=> [2,8,11,7],

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 throw the exception error. Also throw the exception error if the ship is already located at the destination port.

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]}}}

7

• 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 of these functions would be the lists and maps modules.

• Submission Instructions

Submit a filehw3.zip through Canvas containing all the files included in the stub but where all required operations have been implemented.

8