case statement about veryl

[dalance]

I want to consider it, but I think the priority is low.

[taichi-ishitani]

Does Expression in case item have no problem for synthesis?

Yes. In fact, our RTL includes this kind of code.

[taichi-ishitani]

Do you plan to add case inside feature?

[dalance]

Instead of default, How about Rust style default?

always_ff (clk) {
    case x {
        0: a = 1;
        1: a = 2;
        2: {
            a = 3;
            b = 4;
        }
        _: a = 4;
    }
}

[taichi-ishitani]

In SysemVerilog, ? and * are used as symbols which mean wildcard. For exmaple: wildcard operator ==?, wildcard index type int a[*].
How about using ? or * instead of _?

[dalance]

I thought default may be a little long. but there is not another problem.
So I'll use default to follow SystemVerilog.

Do you have any other reason to change to ? or *?

[taichi-ishitani]

I simply proposed ? and * as an alternative of _ character. So I have no special reason.

[dalance]

OK. I'll use default at this time.

[taichi-ishitani]

How about introducing case expression less case statement.
Example:

case {
  foo:     a = 1;
  bar:     a = 2;
  default: a = 3;
}

Equivalent code:

case 1 {
  foo:     a = 1;
  bar:     a = 2;
  default: a = 3;
}

This idea is originally from Ruby's case expression.

[dalance]

It looks good. Does Expression in case item have no problem for synthesis?

[dalance]

Expression less case seems to be difficult to parse by LL(k).
This is because

case {  <- Is this `{` case body's start or expression with concatenation?
    foo: a = 1;
}

To avoid this, chanigning case keyword for expression less case is required.

[taichi-ishitani]

I don't care if expression less case feature is not introduced because I just put 1 as a case expression.

[dalance]

I feel case 1 may be bit strange, but I have no idea about alternative keyword.
So I'll keep the current implementation until new idea.

[taichi-ishitani]

Introduce other keyword insead of case? For example, switch, branch..?

[dalance]

switch seems to be good.

[dalance]

The idea of switch statement moved to #643.