Assignment of code block into Val - scala

Question

I am having hard time understanding this syntax,
val grid = {
val input = """ 08 02 22 97 38 15 00 40 00 75 04 05 07 78 52 12 50 77 91 08
|49 49 99 40 17 81 18 57 60 87 17 40 98 43 69 48 04 56 62 00
|81 49 31 73 55 79 14 29 93 71 40 67 53 88 30 03 49 13 36 65
|52 70 95 23 04 60 11 42 69 24 68 56 01 32 56 71 37 02 36 91
|22 31 16 71 51 67 63 89 41 92 36 54 22 40 40 28 66 33 13 80
|24 47 32 60 99 03 45 02 44 75 33 53 78 36 84 20 35 17 12 50
|32 98 81 28 64 23 67 10 26 38 40 67 59 54 70 66 18 38 64 70
|67 26 20 68 02 62 12 20 95 63 94 39 63 08 40 91 66 49 94 21
|24 55 58 05 66 73 99 26 97 17 78 78 96 83 14 88 34 89 63 72
|21 36 23 09 75 00 76 44 20 45 35 14 00 61 33 97 34 31 33 95
|78 17 53 28 22 75 31 67 15 94 03 80 04 62 16 14 09 53 56 92
|16 39 05 42 96 35 31 47 55 58 88 24 00 17 54 24 36 29 85 57
|86 56 00 48 35 71 89 07 05 44 44 37 44 60 21 58 51 54 17 58
|19 80 81 68 05 94 47 69 28 73 92 13 86 52 17 77 04 89 55 40
|04 52 08 83 97 35 99 16 07 97 57 32 16 26 26 79 33 27 98 66
|88 36 68 87 57 62 20 72 03 46 33 67 46 55 12 32 63 93 53 69
|04 42 16 73 38 25 39 11 24 94 72 18 08 46 29 32 40 62 76 36
|20 69 36 41 72 30 23 88 34 62 99 69 82 67 59 85 74 04 36 16
|20 73 35 29 78 31 90 01 74 31 49 71 48 86 81 16 23 57 05 54
|01 70 54 71 83 51 54 69 16 92 33 48 61 43 52 01 89 19 67 48 """
.stripMargin
val rows = input.split("\n").map(_.trim)
rows.map(_.split(" ").map(_.toInt))
}
Here grid is of type Array[Array[Int]]> I understand that we are creating a 2D array based on some logic inside {} of grid. But what is this val grid = {}, and how can we do calculations inside of it.

Answer 1

In Scala, everything is an expression, and you can combine any sequence of expressions at basically any position in the program.
So here, we assign something to grid, that something is the content of the {} block expression. You can have arbitrary sequences of expressions in a block expression, so in your example we start by definining two val, mostly to make the code easier to read.
Then the last expression, which perform a map on the previously defined rows is the expression returned by the block. That is the value that will be assigned to grid.
A good reason to do such a thing here, is that both input and rows are only visible in the block where they are defined. That means they will not be polluting the scope where you use grid. It's actually very good style.

Answer 2

As method declarations (def) are allowed to have a Block Expression defined to them, so does a Value Declaration.
If we look into the specification (6.11) under "Block", we can see the definition for a valid block declaration:
A block expression { s1; ……; sn; e} is constructed from a sequence
of block statements s1,…,sn and a final expression e. The
statement sequence may not contain two definitions or declarations
that bind the same name in the same namespace. The final expression
can be omitted, in which case the unit value () is assumed.
The expected type of the final expression e is the expected type of
the block. The expected type of all preceding statements is undefined.
And then goes to specify the definition for a value block declaration:
A locally defined value definition val x: T = e is bound by the
existential clause val x: T
Evaluation of the block entails evaluation of its statement sequence,
followed by an evaluation of the final expression e, which defines
the result of the block.
This shows that block expression is valid for member declaration as well as for methods. This is particularly useful when you have a block of code which is relevant only to the initialization of the member, allowing you to create a more complex initialization sequence.