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Usage of and(&) operator in grammar rule [message #1802635]

Wed, 13 February 2019 00:06

Eclipse User

Dear All,

In some of the example i observed that, the & operator used inside the rule definition, could any one clarify why and when to use this & operator in rule definition instead of OR(|).

Example
('resolution' resolution=NumberConstant)?
& ('unit' unit=STRING)?
& ('offset' offset=NumberConstant)?
& (range=RangeSpec)?

In the above example each feature is separated by & operator, so why and when we usually apply/use such operator in rule definition

Thank you

Re: Usage of and(&) operator in grammar rule [message #1802636 is a reply to message #1802635]

Wed, 13 February 2019 00:32

Eclipse User

From the docs

Quote:

Unordered Groups
The elements of an unordered group can occur in any order, but each element must appear once. Members of unordered groups are separated by &.

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