Match Expressions
The syntactical precedence of match expressions has been changed. match
is still a keyword, but it is used like an alphabetical operator. This has several consequences:
-
match
expressions can be chained:xs match { case Nil => "empty" case _ => "nonempty" } match { case "empty" => 0 case "nonempty" => 1 }
(or, dropping the optional braces)
xs match case Nil => "empty" case _ => "nonempty" match case "empty" => 0 case "nonempty" => 1
-
match
may follow a period:if xs.match case Nil => false case _ => true then "nonempty" else "empty"
-
The scrutinee of a match expression must be an
InfixExpr
. Previously the scrutinee could be followed by a type ascription: T
, but this is no longer supported. Sox : T match { ... }
now has to be written(x: T) match { ... }
.
Syntax
The new syntax of match expressions is as follows.
InfixExpr ::= ...
| InfixExpr MatchClause
SimpleExpr ::= ...
| SimpleExpr ‘.’ MatchClause
MatchClause ::= ‘match’ ‘{’ CaseClauses ‘}’
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