Need help with Implementing a simple planner in Julia in the context of the blocks world

Moreno · July 12, 2020, 9:09am

Consider a collection of blocks and several tables. A block A can be in the box or on
one of the tables at a given time. While on a table, a block A can be on the surface of the table or
on top of another block B. The following actions are possible:

put a block A on a table;
put a block A on top of a block B.
Note that putting a block on a table is possible if the block is in the box or on top of another block
on the same table. As well, putting a block on top of another block requires the former block to be
on the same table as the latter. Finally, there is a limit to the number of blocks one can have on
the surface of a given table.
Your task is to write a Julia program that fulfils the following functionality:
accepts a user input that defines the world (how many blocks and how many tables) and a
goal (final layout of blocks on the tables) and generates a plan1
to achieve the goal;
accepts a user input that defines the world, a goal and the current configuration (the current
layout of blocks on the tables) and generates a plan to achieve the goal.

Tamas_Papp · July 13, 2020, 8:36am

Is this a homework problem?

If yes, does the course specify/suggest a set of packages to use for this, or do you need to code the logic from scratch?

Can you show us an attempt at the solution?

Moreno · July 13, 2020, 6:48pm

Hi, Thanks for your reply.

Yes it is a home work. No, the course doesn’t specify any packages to be used.
I am new in Julia, so am kinder lost. I would appreciate if you assist.

Henrique_Becker · July 13, 2020, 11:08pm

Can you be a little more specific on how you are lost? Are you having trouble finding good Julia tutorials? Which other language you know? The problem is the datastructures for the problem? Reading input from the terminal?

Tamas_Papp · July 14, 2020, 5:52am

Your best chance of getting help on this forum is showing some work, explaining where you got stuck, and asking specific questions with code.

I am assuming that you got some kind of introduction to Julia programming in this course. Also, there may be local resources you can turn to to get started, eg a TA. I would try those first.

Moreno · July 14, 2020, 5:56am

Thanks for your feedback.
I am a new bie in Julia. I have knowledge of C#. my main challenge is implementing the Algorithms like Say the Markov Process or BFS to solve the problem.

Moreno · July 14, 2020, 5:58am

Thanks for your feedback .

Yes, i have started with some code will soon post the here for further assistance.
Could possibly share a link to the TA.I? thanks a million for your support

Tamas_Papp · July 14, 2020, 6:00am

TA is short for “teaching assistant”, I am assuming your course has one.

Moreno · July 14, 2020, 6:09am

Unfortunately we don’t have that.

Moreno · July 15, 2020, 7:28am

Hi, so i have tried to prompt the tables and the blocks from the user and now am stuck with how to implement the preconditions, and the goal. Also, i have attempted to write the depth Search to fit my scenario but some how am stuck . Here is my code

using Statistics

using Random

println(“-----------------------”)

println(“- BLOCK WORLD PLANNER -”)

println(“-----------------------”)

print(“”)

function initialState()

#prompt number of tables

print("Enter number of tables : ")

teb = chomp(readline())

global num_tables = parse(Int, teb)

#Collection to store tables in array

global tableCollection = Array{String}(undef, num_tables)

for i ∈ 1:num_tables #

    println()

    print("Enter Table $i : ")

    tableCollection[i] = chomp(readline()) #prompt tables 

    println()  

end

println("#####################################")

print("Enter number of Blocks: ")

blc = chomp(readline())

global num_blocks = parse(Int, blc)

global blockCollection = Array{String}(undef, num_blocks)

for i ∈ 1:num_blocks 

    println()

    print("Enter Block  $i  : ")

    blockCollection[i] = chomp(readline()) #blocks

    

end

#return tableCollection,blockCollection

end

######################################################

function problem_generator(tableCollection, blockCollection)

l = tableCollection

b = collect('A':'Z')

list_blocks = 3

end

#####################################################

function bredthFirstSearch(initialState,goalState)

queue=[]

noOfExpadedNodes = 0

queue.append(initialState)

while queue

    currentState = queue.pop(0)

    #print new queue is

    #print"searching at",currentState.depth

    if currentState.isGoal(goalState)

        #print"goal"

        #print str(currentState)

        return noOfExpadedNodes,currentState

    end

    noOfExpadedNodes = noOfExpadedNodes + 1

    newStateList = currentState.getNewState()

    for newSate in newStateList

        queue.append(newSate)

        newSate.prevState = currentState

        newSate.depth = currentState.depth + 1

    end

    return -1,-1

end

end

Tamas_Papp · July 15, 2020, 7:40am

Are you sure this is meant to be Julia code? It looks like C++ or similar.

Moreno · July 15, 2020, 8:44am

Like i said i am a newbie in julia

Moreno · July 15, 2020, 8:46am

Yes its a julia code

Per · July 15, 2020, 10:56am

In Julia, you typically don’t write objectA.function(objectB). (You could write that, but only if you have a reason to store a function in an object.)

The normal Julia syntax would be function(objectA, objectB). The first argument does not play any special role in Julia like it does in many object oriented languages.

In your specific case the code currentState.isGoal(goalState) should therefore probably read isGoal(currentState, goalState). However, it seems the function isGoal is not yet defined in your code.

Also, to make your code look nice, put tripple backticks around it in your post, like this:

```
function foo(x)
    sqrt(5x)
end
```

This will make it show up with syntax highlighting

function foo(x)
    sqrt(5x)
end

Moreno · July 15, 2020, 10:52pm

Thank you for your reply man.

Moreno · July 15, 2020, 11:08pm

So i came out with this approach of prompting all the blocks and tables from the keyboard and store them in some random arrays which can act as an initial state or problem and later the goal is to have this blocks arranged in tables in an alphabetical order using Backward Search the program should make all the preconditions true using backwards checking and , then it will use forward checking to get to the goal state.

Moreno · July 16, 2020, 12:45am

Hi guys as i explained above, the function initialState prompts the tables and blocks from the keyboard and store them in array and later define the goal State of how the blocks were suppose to be arranged on tables.
now i would like to implement backtracking(Depth First search ) and fowardtraking (Breadth First search ) algorithms to get to the goal defined in the initialState functions any help on how i should implement this algorithms in julia? and also i would lie to have the following preconditions to be evaluated to true to guide my program
‘’‘[“clearTable”,“pickUp”,“putInBox”,“putOnTable”,“putOnTop”,“moveToTable”,“on”]’‘’


    #prompt number of tables

    print("Enter number of tables : ")

    teb = chomp(readline())

    global num_tables = parse(Int, teb)

    #Collection to store tables in array

    global tableCollection = Array{String}(undef, num_tables)

    for i ∈ 1:num_tables #

        println()

        print("Enter Table $i : ")

        tableCollection[i] = chomp(readline()) #prompt tables 

        println()  

    end

    println("*************************************")

    print("Enter number of Blocks: ")

    blc = chomp(readline())

    global num_blocks = parse(Int, blc)

    global blockCollection = Array{String}(undef, num_blocks)

    for i ∈ 1:num_blocks 

        println()

        print("Enter Block  $i  : ")

        blockCollection[i] = chomp(readline()) #blocks

        

    end

    #return tableCollection,blockCollection

    println("*********************************************")

    println("**  Initial state configuration of blocks  **")

    println("*********************************************")

    for i ∈ 1:num_blocks

        println(blockCollection[i])

    end

    println("")

    println("***********************")

    println("**  Number of tables **")

    println("***********************")

    for i ∈ 1:num_tables

        println(tableCollection[i])

    end

    println("**********************")

    println("")

    println("*******************")

    println("**  Goal state  ***")

    println("*******************")

    goalState = sort!(blockCollection)

    print(goalState)

    println("****************")

end```

Tamas_Papp · July 16, 2020, 10:25am

I would suggest you break up your problem to a small set of functions manipulating the state of the world and the planner, each doing one little thing, and then test and develop with variables that represent inputs, and see if they return the desired output, and then combine them.

Reading user input from the command line is probably the last thing I would write.

This is not my field so I am sorry but I cannot help with the specifics, but if I wanted to learn classic AI in Julia, I would just implement everything in

Norvig, Peter. Paradigms of artificial intelligence programming: case studies in Common LISP . Morgan Kaufmann, 1992.

in Julia (using Vectors for flat lists, and other appropriate structures instead of CONSes, but the algorithms are pretty easy to port).

I am curious what resources you were assigned for this course, can you link the course website or a syllabus?