Sorry my examples where so lambda heavy, I did that support first, because
LambdaExpression is ‘special’, as you know Casey.
On October 24, 2017 at 11:30:33, Casey Stella (ceste...@gmail.com) wrote:
So, I do like it. My only issue is the explicit lambda syntax in the
values there (e.g. foo == 0 : () -> true) I'm afraid that when we migrate
to a less explicit lambda syntax ( foo == 0 : true ), we will cause people
to have to transition twice in a row.
Also, it goes without saying, but the syntax must be short-circuiting IMO.
Casey
On Tue, Oct 24, 2017 at 11:26 AM, Kyle Richardson <kylerichards...@gmail.com
> wrote:
> I like the way you have this laid out. Very useful to see it in test
cases.
> I'm +1 for this syntax addition.
>
> -Kyle
>
> On Mon, Oct 23, 2017 at 4:16 PM, Otto Fowler <ottobackwa...@gmail.com>
> wrote:
>
> > What I would like to do for the first PR is introduce match with the
> > following syntax
> >
> >
> > match{ logical expression : transformation expression, ….. , default :
> > transformation expression}
> >
> > Such that the following work for example:
> >
> > @Test
> > public void testMatch() {
> > Assert.assertTrue(runPredicate("match { 1 >= 0 : ()-> true }", new
> > HashMap(){{
> > put("foo", 0);
> > }}));
> > Assert.assertTrue(runPredicate("match { foo == 0 : ()-> true,
> > default : ()-> false }", new HashMap(){{
> > put("foo", 0);
> > }}));
> > Assert.assertFalse(runPredicate("match { foo == 0 : ()-> true,
> > default : ()-> false }", new HashMap(){{
> > put("foo", 1);
> > }}));
> >
> > Assert.assertTrue(runPredicate("match { foo == 0 : ()-> false, foo
> > == 1 : ()-> true, default : ()-> false }", new HashMap(){{
> > put("foo", 1);
> > }}));
> >
> > Assert.assertTrue(runPredicate("match { foo == 0 : ()-> bFalse, foo
> > == 1 : ()-> bTrue, default : ()-> bFalse }", new HashMap(){{
> > put("foo", 1);
> > put("bFalse", new Boolean(false));
> > put("bTrue", new Boolean(true));
> > }}));
> >
> > Assert.assertTrue(runPredicate("match { foo == 0 : ()-> bFalse, foo
> > == 1 : ()-> bTrue, default : ()-> bFalse }", new HashMap(){{
> > put("foo", 1);
> > put("bFalse", new Boolean(false));
> > put("bTrue", new Boolean(true));
> > }}));
> >
> > Assert.assertTrue(runPredicate("match { foo == 0 : bFalse, foo == 1
> > : bTrue, default : false }", new HashMap(){{
> > put("foo", 1);
> > put("bFalse", new Boolean(false));
> > put("bTrue", new Boolean(true));
> > }}));
> >
> > Assert.assertTrue(runPredicate("match { foo == 0 OR bar == 'yes' :
> > ()-> true, default : ()-> false }", new HashMap(){{
> > put("foo", 1);
> > put("bar", "yes");
> > }}));
> >
> > Assert.assertEquals("warning", run("match{ threat.triage.level < 10
> > : 'info', threat.triage.level < 20 : 'warning', default : 'critical'
> > }", new HashMap(){{
> > put("threat.triage.level", 15);
> > }}));
> > }
> >
> >
> > So, the transformation expression will include support for zero arg
> lambda
> > syntax. The work to support the AS aliasing statement and lambda
support
> > for parameters may page in assignment and some other things,
> > and I would like to make that a follow on with some discussion after
> > review.
> >
> > Thoughts?
> >
> >
> >
> > On October 17, 2017 at 14:31:07, Otto Fowler (ottobackwa...@gmail.com)
> > wrote:
> >
> > OK
> >
> >
> > On October 17, 2017 at 14:28:02, Casey Stella (ceste...@gmail.com)
> wrote:
> >
> > Yeah, default would be a keyword. We could also do match(variable1 as
x,
> > variable2 as y) if you want to alias your fields *or* you could do
match
> {
> > ... } if you dont' want to alias your variables.
> >
> > e.g. if you had a field threat.triage.level either of these would work:
> >
> > match(threat.triage.level -> x) { x < 10 : 'info', x < 20 : 'warning',
> > default : 'critical' }
> > OR
> > match { threat.triage.level < 10 : 'info', threat.triage.level < 20 :
> > 'warning, default : 'critical' }
> >
> >
> >
> > On Tue, Oct 17, 2017 at 2:24 PM, Otto Fowler <ottobackwa...@gmail.com>
> > wrote:
> >
> > > No that is it.
> > >
> > > So default would be a keyword?
> > >
> > > and a lambda that uses x can be used on the right side of the :
> > >
> > >
> > >
> > > On October 17, 2017 at 14:21:01, Casey Stella (ceste...@gmail.com)
> > wrote:
> > >
> > > So, just to map this onto the example, you mean:
> > > match(longer_variable -> x) { x < 10 : 'info', x <= 20 : 'warn',
> default:
> > > 'critical' } ? I took the liberty of adding a default keyword there
> the
> > > evaluation of the conditionals are considered lambda functions also.
> > >
> > > Did I catch the spirit of the suggestion or did I miss anything?
> > >
> > > On Tue, Oct 17, 2017 at 2:18 PM, Otto Fowler <ottobackwa...@gmail.com>
> > > wrote:
> > >
> > >> How about this:
> > >>
> > >> match(VAR_TO_VAL_ASSIGNMENT+) { BOOLEAN_STATEMENT(VALS) :
> LAMBDA(VALS),
> > >> BOOLEAN_STATEMENT(VALS) : LAMBDA(VALS) , LAMBDA(VALS)}
> > >>
> > >> * match = new keyword
> > >> * match takes variable number of assignments, where the val assigned
> to
> > >> is available in the evaluation and the lambdas
> > >> * match {} contains comma separated list of a statement that
evaluates
> > to
> > >> a boolean and a lambda
> > >> * LAMBDA is executed on match, and it’s value is returned
> > >> * no matches returns null or return of optional final statement,
which
> > is
> > >> a LAMBDA without a BOOLEAN_STATEMENT
> > >>
> > >>
> > >> On October 17, 2017 at 12:06:05, Casey Stella (ceste...@gmail.com)
> > wrote:
> > >>
> > >> Ugh, I forgot to preface this with DISCUSS: Sorry!
> > >>
> > >> On Tue, Oct 17, 2017 at 12:05 PM, Casey Stella <ceste...@gmail.com>
> > >> wrote:
> > >>
> > >> > Hi All,
> > >> >
> > >> > It's high time that Stellar supports some form of conditional that
> is
> > >> > beyond if/then/else. Right now, the way to do fall-through
> > conditionals
> > >> is:
> > >> >
> > >> > if x < 10 then 'info' else if x >= 10 && x <= 20 then 'warn' else
> > >> > 'critical'
> > >> >
> > >> > That becomes non-scalable very quickly. I wanted to facilitate a
> > >> > discussion with the community on the syntax. I'll give a few
options
> > and
> > >> > you guys/gals can come up with your own suggestions too, but I
> wanted
> > to
> > >> > frame teh conversation.
> > >> >
> > >> > *MAP-BASED SWITCH*
> > >> >
> > >> > With the advent of METRON-1254 (https://github.com/apache/met
> > >> ron/pull/801),
> > >> > we could enable (from a language perspective in Stellar)
multi-part
> > >> > conditionals or switch/case style statements. To wit:
> > >> >
> > >> > MAP_GET(true, { x < 10 : 'info', x >= 10 && x <= 20 : 'warn', x >
> 20 :
> > >> > 'critical' })
> > >> >
> > >> > Or, with a convenience function:
> > >> >
> > >> > CASE( { x < 10 : 'info', x >= 10 && x <= 20 : 'warn', x > 20 :
> > >> 'critical'
> > >> > } )
> > >> >
> > >> > The issue with this is that the last true condition wins because
> we're
> > >> > using a map.
> > >> >
> > >> > *LIST-BASED SWITCH*
> > >> >
> > >> > We could correct this by adding a list of pairs construction to
> > stellar:
> > >> >
> > >> > CASE( [ x < 10 : 'info', x <= 20 : 'warn'], 'critical')
> > >> >
> > >> > This would enable us to allow the first true condition to win, so
> the
> > >> > second condition can be simpler and we could pass a default return
> > >> value as
> > >> > the final argument.
> > >> > The downside to this, is that it requires a language enhancement
> (the
> > >> list
> > >> > of pairs construction you see there).
> > >> >
> > >> > *LAMBDA FUNCTION-BASED SWITCH*
> > >> >
> > >> > Some of the problems with the previous statements are that every
> > >> > conditional has to be evaluated and there is no opportunity to
short
> > >> > circuit. They're all evaluated at parse-time rather than execution
> > time.
> > >> > We could, instead, construct a lambda function approach to this
and
> > >> support
> > >> > short-circuiting in even complex conditionals:
> > >> >
> > >> > CASE( real_variable_name, [ x -> x < 10 ? 'info', x -> x <= 20 ?
> > 'warn'
> > >> ],
> > >> > 'critical')
> > >> > or
> > >> > CASE( real_variable_name, [ x -> if x < 10 then 'info', x -> if x
<=
> > 20
> > >> > then 'warn' ], 'critical')
> > >> >
> > >> > This would require lessening ?: (if/then/else) syntax to support
to
> > >> enable
> > >> > just if without else conditions. This also has the benefit of
> allowing
> > >> > simplifying the expression due to lambda function variable
renaming
> > >> > (real_variable_name can be much more complex (or even an
expression)
> > >> than
> > >> > 'x'.
> > >> >
> > >> > Creative other approaches to this are appreciated!
> > >> >
> > >> > Thanks,
> > >> >
> > >> > Casey
> > >> >
> > >>
> > >>
> > >
> >
>
