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.
- The right hand side of entry definitions can be empty.
(Useful for deleting "filler" phrases.)
- 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.
- 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
- 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.)
- 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. (?)
- 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. (?)
- 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