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2

I have an integer matrix of n rows by m cols representing a game board, and have written two functions that allow me to retrieve and set values within the matrix.

let get_val board (row, col) = 
 if row < 0 
 || col < 0 
 || (Array.length data) < (row + 1) 
 || (Array.length data.(row)) < (col + 1)
 then None
 else if (board.(row).(col)) = (-1)
 then None
 else Some (board.(row).(col)) ;;

let set_val board (row, col) i = 
 if row < 0 
 || col < 0 
 || (Array.length data) < row+1
 || (Array.length data.(row)) < col+1
 || i < 0
 then invalid_arg "set: invalid arguments"
 else board.(row).(col) <- i;
 board ;;

let board = Array.make_matrix 4 4 ;;

All positions are set to -1 initially to represent an empty square. Basically, if I try to retrieve a value outside of the board, I get a None. If the location is valid and not an empty square, I get can retrieve the value at that matrix as a Some type. I would like to increment a position by 1 in a board by using these two functions.

My first attempt in the board by 1 by doing the following:

let board = set_val board (2, 2) ((get_val board (2, 2)) + 1)

However, I run into the type issue,

This expression has type int option but an expression was expected of type int 

, which I understand is because "get_val" returns a Some type, and 1 is an integer. I also tried:

let board = set_val board (2, 2) ((get_val board (2, 2)) + (Some 1))

, but board is an integer matrix. The constraints of the problem require me to return a Some/None from "get_val", but I need a way to retrieve the values from the function "get" as an int, not a Some. I've looked into how to convert from an Option to an int, but came up with nothing, since I'm not allowed access to the Option module. I suspect I'm not looking up the correct thing, but have run out of places to look. How would I be able to use the result of "get_val" in a way that I can increment the new value for a position on the board?

ocaml

share|improve this question

asked Mar 25 at 2:23

Alex PenizAlex Peniz

205

add a comment | 

2

I have an integer matrix of n rows by m cols representing a game board, and have written two functions that allow me to retrieve and set values within the matrix.

let get_val board (row, col) = 
 if row < 0 
 || col < 0 
 || (Array.length data) < (row + 1) 
 || (Array.length data.(row)) < (col + 1)
 then None
 else if (board.(row).(col)) = (-1)
 then None
 else Some (board.(row).(col)) ;;

let set_val board (row, col) i = 
 if row < 0 
 || col < 0 
 || (Array.length data) < row+1
 || (Array.length data.(row)) < col+1
 || i < 0
 then invalid_arg "set: invalid arguments"
 else board.(row).(col) <- i;
 board ;;

let board = Array.make_matrix 4 4 ;;

All positions are set to -1 initially to represent an empty square. Basically, if I try to retrieve a value outside of the board, I get a None. If the location is valid and not an empty square, I get can retrieve the value at that matrix as a Some type. I would like to increment a position by 1 in a board by using these two functions.

My first attempt in the board by 1 by doing the following:

let board = set_val board (2, 2) ((get_val board (2, 2)) + 1)

However, I run into the type issue,

This expression has type int option but an expression was expected of type int 

, which I understand is because "get_val" returns a Some type, and 1 is an integer. I also tried:

let board = set_val board (2, 2) ((get_val board (2, 2)) + (Some 1))

, but board is an integer matrix. The constraints of the problem require me to return a Some/None from "get_val", but I need a way to retrieve the values from the function "get" as an int, not a Some. I've looked into how to convert from an Option to an int, but came up with nothing, since I'm not allowed access to the Option module. I suspect I'm not looking up the correct thing, but have run out of places to look. How would I be able to use the result of "get_val" in a way that I can increment the new value for a position on the board?

ocaml

share|improve this question

asked Mar 25 at 2:23

Alex PenizAlex Peniz

205

add a comment | 

I have an integer matrix of n rows by m cols representing a game board, and have written two functions that allow me to retrieve and set values within the matrix.

let get_val board (row, col) = 
 if row < 0 
 || col < 0 
 || (Array.length data) < (row + 1) 
 || (Array.length data.(row)) < (col + 1)
 then None
 else if (board.(row).(col)) = (-1)
 then None
 else Some (board.(row).(col)) ;;

let set_val board (row, col) i = 
 if row < 0 
 || col < 0 
 || (Array.length data) < row+1
 || (Array.length data.(row)) < col+1
 || i < 0
 then invalid_arg "set: invalid arguments"
 else board.(row).(col) <- i;
 board ;;

let board = Array.make_matrix 4 4 ;;

All positions are set to -1 initially to represent an empty square. Basically, if I try to retrieve a value outside of the board, I get a None. If the location is valid and not an empty square, I get can retrieve the value at that matrix as a Some type. I would like to increment a position by 1 in a board by using these two functions.

My first attempt in the board by 1 by doing the following:

let board = set_val board (2, 2) ((get_val board (2, 2)) + 1)

However, I run into the type issue,

This expression has type int option but an expression was expected of type int 

, which I understand is because "get_val" returns a Some type, and 1 is an integer. I also tried:

let board = set_val board (2, 2) ((get_val board (2, 2)) + (Some 1))

, but board is an integer matrix. The constraints of the problem require me to return a Some/None from "get_val", but I need a way to retrieve the values from the function "get" as an int, not a Some. I've looked into how to convert from an Option to an int, but came up with nothing, since I'm not allowed access to the Option module. I suspect I'm not looking up the correct thing, but have run out of places to look. How would I be able to use the result of "get_val" in a way that I can increment the new value for a position on the board?

ocaml

share|improve this question

asked Mar 25 at 2:23

Alex PenizAlex Peniz

205

let get_val board (row, col) = 
 if row < 0 
 || col < 0 
 || (Array.length data) < (row + 1) 
 || (Array.length data.(row)) < (col + 1)
 then None
 else if (board.(row).(col)) = (-1)
 then None
 else Some (board.(row).(col)) ;;

let set_val board (row, col) i = 
 if row < 0 
 || col < 0 
 || (Array.length data) < row+1
 || (Array.length data.(row)) < col+1
 || i < 0
 then invalid_arg "set: invalid arguments"
 else board.(row).(col) <- i;
 board ;;

let board = Array.make_matrix 4 4 ;;

let board = set_val board (2, 2) ((get_val board (2, 2)) + 1)

This expression has type int option but an expression was expected of type int 

let board = set_val board (2, 2) ((get_val board (2, 2)) + (Some 1))

share|improve this question

asked Mar 25 at 2:23

Alex PenizAlex Peniz

205

share|improve this question

asked Mar 25 at 2:23

Alex PenizAlex Peniz

205

asked Mar 25 at 2:23

Alex PenizAlex Peniz

205

asked Mar 25 at 2:23

Alex PenizAlex Peniz

205

1 Answer
1

active

oldest

votes

1

The best/idiomatic Ocaml way to do this is using pattern matching.

let board = match (S.get grid (row, col)) with 
 | None -> S.set grid (row, col) 1
 | Some v -> S.set grid (row, col) (v+1)

Apparently, this way you can strip the Some part of the v and just get the actual value.

share|improve this answer

edited Mar 27 at 10:54

Sir E_net4 the Downvoter

13.7k74077

answered Mar 25 at 3:11

Alex PenizAlex Peniz

205

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  It would be cleaner to store an int option in the board instead of misusing -1 as None. But if the board is gigantic then memory requirement might make that necessary.
  
  – Goswin von Brederlow
  Mar 25 at 12:31
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Naps and shower are the best way to think about problems.
  
  – Richard-Degenne
  Mar 26 at 12:58
  

  
  
  
  

add a comment | 

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1

The best/idiomatic Ocaml way to do this is using pattern matching.

let board = match (S.get grid (row, col)) with 
 | None -> S.set grid (row, col) 1
 | Some v -> S.set grid (row, col) (v+1)

Apparently, this way you can strip the Some part of the v and just get the actual value.

share|improve this answer

edited Mar 27 at 10:54

Sir E_net4 the Downvoter

13.7k74077

answered Mar 25 at 3:11

Alex PenizAlex Peniz

205

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  It would be cleaner to store an int option in the board instead of misusing -1 as None. But if the board is gigantic then memory requirement might make that necessary.
  
  – Goswin von Brederlow
  Mar 25 at 12:31
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Naps and shower are the best way to think about problems.
  
  – Richard-Degenne
  Mar 26 at 12:58
  

  
  
  
  

add a comment | 

1

The best/idiomatic Ocaml way to do this is using pattern matching.

let board = match (S.get grid (row, col)) with 
 | None -> S.set grid (row, col) 1
 | Some v -> S.set grid (row, col) (v+1)

Apparently, this way you can strip the Some part of the v and just get the actual value.

share|improve this answer

edited Mar 27 at 10:54

Sir E_net4 the Downvoter

13.7k74077

answered Mar 25 at 3:11

Alex PenizAlex Peniz

205

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  It would be cleaner to store an int option in the board instead of misusing -1 as None. But if the board is gigantic then memory requirement might make that necessary.
  
  – Goswin von Brederlow
  Mar 25 at 12:31
  
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Naps and shower are the best way to think about problems.
  
  – Richard-Degenne
  Mar 26 at 12:58
  

  
  
  
  

add a comment | 

The best/idiomatic Ocaml way to do this is using pattern matching.

let board = match (S.get grid (row, col)) with 
 | None -> S.set grid (row, col) 1
 | Some v -> S.set grid (row, col) (v+1)

Apparently, this way you can strip the Some part of the v and just get the actual value.

share|improve this answer

edited Mar 27 at 10:54

Sir E_net4 the Downvoter

13.7k74077

answered Mar 25 at 3:11

Alex PenizAlex Peniz

205

let board = match (S.get grid (row, col)) with 
 | None -> S.set grid (row, col) 1
 | Some v -> S.set grid (row, col) (v+1)

share|improve this answer

edited Mar 27 at 10:54

Sir E_net4 the Downvoter

13.7k74077

answered Mar 25 at 3:11

Alex PenizAlex Peniz

205

edited Mar 27 at 10:54

Sir E_net4 the Downvoter

13.7k74077

edited Mar 27 at 10:54

Sir E_net4 the Downvoter

13.7k74077

answered Mar 25 at 3:11

Alex PenizAlex Peniz

205

answered Mar 25 at 3:11

Alex PenizAlex Peniz

205