Scala: if-else expression as left operand, operation is performed only if condition evaluates to fal-CodePudding

Like the following example:

scala> if (true) { 1 } else { 2 }   3
val res1: Int = 1

scala> if (false) { 1 } else { 2 }   3
val res2: Int = 5

It seems as if the curly braces are ignored. Wrapping the if-else expression with parentheses seems to work as expected.

scala> (if (true) { 1 } else { 2 })   3
val res3: Int = 4

This appears super unintuitive to me. Can someone please help me understand this?

CodePudding user response：

The intuition is that braces simply create a block expression that can be part of a larger expression. They are not part of the if statement.

The general form of if is

if (<test>) <expression> else <expression>

In the question the code after the else is a simple expression:

{ 2 }   3

has a higher precedence than if/else so it is parsed as

if (<test>) { 1 } else ({ 2 }   3)

rather than

(if (<test>) { 1 } else { 2 })   3