[rules-dev] Summary of all new features in DSL - comments, please

[Wolfgang Laun]

This is a summary of the currently implemented new features for the DSL
expansion. I'll have to add tests and documentation, but before doing so,
I'd like to learn whether there are any objections (resulting in the
removal) or suggestions for improvement. Myself, I'm not sure about one or
two items which I've marked with "(?)". Also, there's a couple of items
which might gain from easy-to-implement additions, see "Votes, please". An
example showing most of the new options is given below.

   1. The right hand side of entry definitions can be empty. (Useful for
   deleting "filler" phrases.)
   2. Long entry lines can be split without the need of escaping EOL:
      - Any line beginning with # or // starts a DSL comment and is not
      passed to the DSL parser.
      - Any line beginning with '[' starts a new entry.
      - All other lines are appended to the preceding line, with a space
      replacing EOL.
      - Empty lines are inserted to maintain original line numbers, and line
      and column numbers in error messages from the parser are recalculated to
      reflect the user view of the DSL text.
   3. The special comment introduction "#/" is used to mark a line
   containing debug options. Currently recognized keywords are:
      - result - dumps the resulting DRL
      - steps - shows all expansion operations in conditions and
      consequences
      - keyword, when, then - display the corresponding entry definitions
      - usage - shows how often an entry was actually used in an expansion
   4. Variable substitution uses the definition of that variable seen last
   in the current when or then part expansion. not just from the current line.
   (But this probably should keep variables from the when part for the
   following then part. Votes, please.)
   5. The value used in a variable substitution can be modified on the fly
   by adding one of the modifiers after and '!' in the variable reference.
   Currently recognized modifiers are:
      - uc, lc - convert all letters to upper case or lower case,
      respectively
      - ucfirst - convert the first letter to upper case, and all other
      letters to lower case
      - num - extract all digits and a '-' preceding the first digit and
      insert the numeric value; a '.' or ',' two digits from the right
is retained
      as a decimal point, which is useful for monetary quantitites. (?)
   6. Another modification of the value used for substituting the reference
   is by providing a "multiple choice" after an '!', consisting of strings
   separated alternatively by '?' and '/': If the string extracted from the
   DSLR line matches the string before a '?', the string following it is used
   for substitution; otherwise test the next choice. (?)
   7. A DSL value starting with a hyphen ('-') can also be used in a
   consequence to add another setter expression into a preceding "modify(x){}".
   (Should probably be extended to be able to handle the insertion of another
   parameter to any preceding method call and, as a special, but useful, case
   the concatenation to a preceding x.println() or x.print() call. Votes,
   please.)

DSL:
[when][][Tt]here is an?=
[when][]{entity} called {x}=
        ${entity!lc}: {entity!ucfirst}( $name:
name=="{x!M?Mark/E?Edson/G?Geoffrey/unknown}")
[when][]and no other with the same {attr}=not {entity!ucfirst}( {attr} ==
${attr} )
[then][]change person=modify($person)\{\}
[then][]- set {attr} to {value} = set{attr!ucfirst}( {value!num} )

DSLR:
rule "Rule 1"
when
    There is a PERSON called M
    and no other with the same name
then
    change person
    - set salary to US$9,999.99
    - set rank to "colonel"
end

DRL:
   8  rule "Rule 1"
   9  when
  10  $person: Person( $name: name=="Mark")
  11  not Person( name == $name )
  12  then
  13  modify($person){ setSalary( 9999.99 ), setRank( "colonel" ) }
  14  end

Cheers
Wolfgang
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.jboss.org/pipermail/rules-dev/attachments/20101224/c10a7b2b/attachment-0001.html