Guard variable and being effectively final

[forax at univ-mlv.fr]

----- Original Message -----
> From: "cay horstmann" <cay.horstmann at gmail.com>
> To: "Remi Forax" <forax at univ-mlv.fr>, "amber-spec-experts" <amber-spec-experts at openjdk.java.net>
> Sent: Saturday, May 21, 2022 7:50:44 PM
> Subject: Re: Guard variable and being effectively final

> Hi Rémy,
> 
> it compiles with build 19-ea+23-1706 if you replace && with when.

sadly, assigning op also compiles :(

  IntBinaryOperator op = null;

I think the new implementation is missing a check that the local variables after a "when" has to be effectively final

> 
> Also, remove "4" from the list or add an operator :-)

yes

> 
> Cheers,
> 
> Cay

Rémi

> 
> Il 21/05/2022 13:55, Remi Forax ha scritto:
>> interface reverse_polish_notation {
>>    static Map<String, IntBinaryOperator> OPS =
>>        Map.of("+", (a, b) -> a + b, "*", (a, b) -> a * b);
>> 
>>    static int eval(List<String> expr) {
>>      var stack = new ArrayDeque<Integer>();
>>      for(var token: expr) {
>>        final IntBinaryOperator op;
>>        stack.push(switch (token) {
>>          case String __ && (op = OPS.get(token)) != null -> {
>>            var value1 = stack.pop();
>>            var value2 = stack.pop();
>>            yield op.applyAsInt(value1, value2);
>>          }
>>          default -> Integer.parseInt(token);
>>        });
>>      }
>>      return stack.pop();
>>    }
>> 
>>    static void main(String[] args) {
>>      var expr = List.of("1",  "2",  "+", "3", "*", "4");
>>      System.out.println(eval(expr));
>>    }
>> }
> 
> --
> 
> Cay S. Horstmann | http://horstmann.com | mailto:cay at horstmann.com