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Update scala-for-java-programmers.md: Rename l to left for clarity #3050

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Aug 5, 2024
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Update scala-for-java-programmers.md: Rename l to left for clarity #3050

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20 changes: 10 additions & 10 deletions _overviews/tutorials/scala-for-java-programmers.md
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Original file line number Diff line number Diff line change
Expand Up @@ -649,7 +649,7 @@ they can be used to define the type of the trees for our example:
```scala
abstract class Tree
object Tree {
case class Sum(l: Tree, r: Tree) extends Tree
case class Sum(left: Tree, right: Tree) extends Tree
case class Var(n: String) extends Tree
case class Const(v: Int) extends Tree
}
Expand Down Expand Up @@ -682,7 +682,7 @@ but also to implement ADTs. Here is how they can be used to define the type
of the trees for our example:
```scala
enum Tree:
case Sum(l: Tree, r: Tree)
case Sum(left: Tree, right: Tree)
case Var(n: String)
case Const(v: Int)
```
Expand Down Expand Up @@ -750,7 +750,7 @@ Scala as follows, using a pattern match on a tree value `t`:
import Tree._

def eval(t: Tree, ev: Environment): Int = t match {
case Sum(l, r) => eval(l, ev) + eval(r, ev)
case Sum(left, right) => eval(left, ev) + eval(right, ev)
case Var(n) => ev(n)
case Const(v) => v
}
Expand All @@ -762,7 +762,7 @@ def eval(t: Tree, ev: Environment): Int = t match {
import Tree.*

def eval(t: Tree, ev: Environment): Int = t match
case Sum(l, r) => eval(l, ev) + eval(r, ev)
case Sum(left, right) => eval(left, ev) + eval(right, ev)
case Var(n) => ev(n)
case Const(v) => v
```
Expand All @@ -773,12 +773,12 @@ def eval(t: Tree, ev: Environment): Int = t match
You can understand the precise meaning of the pattern match as follows:

1. it first checks if the tree `t` is a `Sum`, and if it
is, it binds the left sub-tree to a new variable called `l` and
the right sub-tree to a variable called `r`, and then proceeds
is, it binds the left sub-tree to a new variable called `left` and
the right sub-tree to a variable called `right`, and then proceeds
with the evaluation of the expression following the arrow; this
expression can (and does) make use of the variables bound by the
pattern appearing on the left of the arrow, i.e., `l` and
`r`,
pattern appearing on the left of the arrow, i.e., `left` and
`right`,
2. if the first check does not succeed, that is, if the tree is not
a `Sum`, it goes on and checks if `t` is a `Var`; if
it is, it binds the name contained in the `Var` node to a
Expand Down Expand Up @@ -841,7 +841,7 @@ obtain the following definition:
import Tree._

def derive(t: Tree, v: String): Tree = t match {
case Sum(l, r) => Sum(derive(l, v), derive(r, v))
case Sum(left, right) => Sum(derive(left, v), derive(right, v))
case Var(n) if v == n => Const(1)
case _ => Const(0)
}
Expand All @@ -853,7 +853,7 @@ def derive(t: Tree, v: String): Tree = t match {
import Tree.*

def derive(t: Tree, v: String): Tree = t match
case Sum(l, r) => Sum(derive(l, v), derive(r, v))
case Sum(left, right) => Sum(derive(left, v), derive(right, v))
case Var(n) if v == n => Const(1)
case _ => Const(0)
```
Expand Down
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