[rules-dev] 2nd call: Summary of all new features in DSL - comments, please

[Wolfgang Laun]

Probably sent not at the best of times, this didn't get a peep from anyone.
Please do comment, for the reasons stated below.
-W

On 24 December 2010 11:23, Wolfgang Laun <wolfgang.laun at gmail.com> wrote:

> 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
>
>
>
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