Scala for loop yield - scala

Question

I'm new to Scala so I'm trying to mess around with an example in Programming in Scala: A Comprehensive Step-by-Step Guide, 2nd Edition
// Returns a row as a sequence
def makeRowSeq(row: Int) =
for (col <- 1 to 10) yield {
val prod = (row * col).toString
val padding = " " * (4 - prod.length)
padding + prod
}
// Returns a row as a string
def makeRow(row: Int) = makeRowSeq(row).mkString
// Returns table as a string with one row per line
def multiTable() = {
val tableSeq = // a sequence of row strings
for (row <- 1 to 10)
yield makeRow(row)
tableSeq.mkString("\n")
}
When calling multiTable() the above code outputs:
1 2 3 4 5 6 7 8 9 10
2 4 6 8 10 12 14 16 18 20
3 6 9 12 15 18 21 24 27 30
4 8 12 16 20 24 28 32 36 40
5 10 15 20 25 30 35 40 45 50
6 12 18 24 30 36 42 48 54 60
7 14 21 28 35 42 49 56 63 70
8 16 24 32 40 48 56 64 72 80
9 18 27 36 45 54 63 72 81 90
10 20 30 40 50 60 70 80 90 100
This makes sense but if I try to change the code in multiTable() to be something like:
def multiTable() = {
val tableSeq = // a sequence of row strings
for (row <- 1 to 10)
yield makeRow(row) {
2
}
tableSeq.mkString("\n")
}
The 2 is being returned and changing the output. I'm not sure where it's being used though to manipulate the output and can't seem to find a similar example searching around here or Google. Any input would be appreciated!

Answer 1

makeRow(row) {2}
and
makeRow(row)(2)
and
makeRow(row).apply(2)
are all equivalent.
makeRow(row) is of type List[String], each String representing one row. So effectively, you are picking character at index 2 from each row. That is why you are seeing 9 spaces and one 1 in your output.
def multiTable() = {
val tableSeq = // a sequence of row strings
for (row <- 1 to 10)
yield makeRow(row) {2}
tableSeq.mkString("\n")
}
is equivalent to applying a map on each row like
def multiTable() = {
val tableSeq = // a sequence of row strings
for (row <- 1 to 10)
yield makeRow(row)
tableSeq.map(_(2)).mkString("\n")
}