Initializing a 2-dimensional array in Scala
(Scala 2.7.7 :) I'm not used to 2d arrays. Arrays are mutable, but how can I specify a 2d array that is, say, 3x4 in size. Dimension (2D) is fixed, but the size of each dimension must be initialized. I've tried this:
class Field (val rows: Int, val cols: Int, sc: java.util.Scanner) {
var field = new Array [Char](rows)(cols)
for (r <- (1 to rows)) {
val line = sc.nextLine ()
val spl = line.split (" ")
field (r) = spl.map (_.charAt (0))
}
def put (row: Int, col: Int, c: Char) =
todo ()
}
I am getting this error:: 11: error: update value is not a member Char field (r) = spl.map (_. CharAt (0))
If it were Java, this would be a lot more code, but I would know how to do it, so I show what I mean:
public class Field
{
private char[][] field;
public Field (int rows, int cols, java.util.Scanner sc)
{
field = new char [rows][cols];
for (int r = 0; r < rows; ++r)
{
String line = sc.nextLine ();
String[] spl = line.split (" ");
for (int c = 0; c < cols; ++c)
field [r][c] = spl[c].charAt (0);
}
}
public static void main (String args[])
{
new Field (3, 4, new java.util.Scanner ("fraese.fld"));
}
}
and fraese.fld would look like this:
M M M
M . M
I am doing several steps with
val field = new Array [Array [Char]](rows)
but how could I implement "put"? Or is there a better way to implement a 2D array. Yes, I could use a one-dimensional matrix and work with
put (y, x, c) = field (y * width + x) = c
but I would prefer a notation that looks more than 2d-ish.
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for (r <- (1 to rows)) {
If it is true:
for (r <- (0 to rows - 1)) {
... starting at 0 instead of 1?
field (r) = spl.map (_.charAt (0))
If it uses operator syntax like:
field (r) = spl map (_.charAt (0))
... without the "." between spl and map?
This is my version - I replaced Scanner with Array [String] as I'm not really sure what the input for the scanner should be. It compiles and runs on Scala 2.7.5:
class Field (val rows: Int, val cols: Int, lines: Array[String]) {
var field = new Array [Array[Char]](rows)
// These get replaced later on, but this is how to initialize a 2D array.
for (i <- (0 to rows - 1)) {
field(i) = new Array[Char](cols)
}
for (r <- (0 to rows - 1)) {
val line = lines(r)
val spl = line.split (" ")
field(r) = spl map (_.charAt (0))
}
}
var lines = Array[String] ("A A A A A", "B B B B B", "C C C C C", "D D D D D", "E E E E E")
var test = new Field(5, 5, lines)
test.field
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