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[Radu Mereuta <headness13 AT gmail.com>]

There is also

syntax EPlus ::= NeList{E, ""} // standing for not empty list

Regarding the others, I'm not sure that we have a convention, I think with SDF all of them work correctly. Just don't forget to add the [left] or [right] attribute:

syntax EPlus ::= E | EPlus EPlus [left]

The difference between List{...} and '__ is that the first one creates a cons list with an empty element that signifies the end of the list. The second one, creates a cons list, but you are responsible of handling it in all cases (empty list, one element, more than one element).

Radu

On Fri, Oct 18, 2013 at 10:29 PM, Park, Daejun <dpark69 AT illinois.edu> wrote:

Hi,

This is my first question as a K user!

When it comes to represent the following syntax, what would be the best practice?

- e? : zero or one

- e* : more than or equal to zero

- e+ : more than zero

What I've been trying is:

syntax EOpt  ::= E | "" [onlyLabel, klabel("'epsilon")]  

syntax EStar ::= List{E, ""}
syntax EPlus ::= ??

Am I right? Or, is there more elegant way?

Also, if I should use either of the follows, which one will be better?

syntax EPlus ::= E | E     EPlus

syntax EPlus ::= E | EPlus EPlus

Thanks in advance!

Daejun

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