Re: [racket-users] Redex - constraining what is used to fill a hole
On Sunday, December 13, 2015, Sam Caldwell wrote:
> > I'm not completely following the design goals here because it seems
> > like the desire to reduce only State-Qs could be achieved by writing
> > rules that reduced only State-Qs (not arbitrary states). Or are you
> > saying that State-Qs are only allowed in the context? If so, then you
> > could write E differently?
>
> I don't think I can constrain the rules to only operate on State-Qs
> because the *outermost* State needs to reduce, and it does not need to
> be a State-Q. I think this would lead to duplicating all of the
> reduction rules; once for the outermost State and once for internal
> State-Qs.
>
Oh I see. You could probably refactor your language grammar to avoid this
but if define-judgment-form is a better fit then by all means do that.
>
> It's not clear to me how I would change the definition of E to achieve
> this.
>
> > you could rewrite it using define-judgment-form
>
> This seems fairly promising - looking at the docs I don't see any
> reason define-judgment-form couldn't do what I want in a
> straightforward manner.
>
> Thanks for the help,
> Sam Caldwell
>
>
> On Sun, Dec 13, 2015 at 5:17 PM, Robby Findler <
> ro...@eecs.northwestern.edu
> > wrote:
>
>> I'm not completely following the design goals here because it seems
>> like the desire to reduce only State-Qs could be achieved by writing
>> rules that reduced only State-Qs (not arbitrary states). Or are you
>> saying that State-Qs are only allowed in the context? If so, then you
>> could write E differently? I think that all of this is expressible
>> without using a feature like you want in Redex, but I'm not really
>> getting precisely what you want so I'm hesitant to make more concrete
>> suggestions.
>>
>> Regardless, if for some reason it is better to express your rewriting
>> relation in the way that has actual premises, then you could rewrite
>> it using define-judgment-form. Relations defined with
>> define-judgment-form that have the mode (I O) or (O I) can be used
>> with 'traces' and 'stepper' (as well as show-derivations).
>>
>> hth,
>> Robby
>>
>>
>> On Sat, Dec 12, 2015 at 8:21 PM, Sam Caldwell > > wrote:
>> > Thanks for clarifying, Robby.
>> >
>> > I'm modeling reduction on nested states. In addition to a collection of
>> > straightforward rules, there is a rule that specifies when to reduce a
>> > state-inside-a-state. I can specify this using evaluation contexts, but
>> in
>> > order for the relation to remain deterministic I need to restrict which
>> > nested-states are reduced to a particular subclass.
>> >
>> > I'm hoping this little model demonstrates what I'm trying to do:
>> >
>> > ==
>> >
>> > #lang racket
>> >
>> > (require redex)
>> >
>> > (define-language L
>> > (State (number
>> > (Event ...) ;; "incoming" events
>> > (Event ...) ;; "outgoing" events
>> > (State ...)))
>> > (Event string)
>> > ;; states with no outgoing events
>> > (State-Q (number
>> > (Event ...)
>> > ()
>> > (State ...)))
>> > ;; states with no incoming or outgoing events
>> > (State-I (number
>> > ()
>> > ()
>> > (State ...)))
>> > ;; Evaluation Contexts
>> > (E hole
>> > (number
>> > ()
>> > (Event ...)
>> > (State-I ... E State-Q ...
>> >
>> > (define red
>> > (reduction-relation
>> >L
>> >;; incoming events just increase a counter
>> >(--> (number
>> > (Event_0 Event_n ...)
>> > (Event ...)
>> > (State ...))
>> > (,(add1 (term number))
>> > (Event_n ...)
>> > (Event ...)
>> > (State ...))
>> > handle)
>> >;; once a State has processed all of its incoming Events, it can
>> receive
>> > an
>> >;; outgoing Event from nested States.
>> >(--> (number
>> > ()
>> > (Event_out ...)
>> > (State-Q ...
>> > (number_s
>> >(Event_si ...)
>> >(Event Event_so ...)
>> >(State_s ...))
>> > State ...))
>> > (number
>> > (Event Event_so ...)
>> > (Event_out ...)
>> > (State-Q ...
>> > (number_s
>> >(Event_si ...)
>> >()
>> >(State_s ...))
>> > State ...))
>> > receive)))
>> >
>> > #|
>> > Want this to result in:
>> > '((5 () () ((4 () () ()) (4 () () ()
>> > |#
>> > (apply-reduction-relation*
>> > red
>> > (term (0 ()
>> > ()
>> > ((1 ("hi" "hello" "ciao")
>> > ("zip" "zap" "zooey")
>> > ())
>> >(2 ("where" "fore")
>> > ("art" "thou")
>> > ())
>> >
>> > ==
>> >
>> > That model allows the top-most State to process incoming Events and
>> receive
>> > Events
Re: [racket-users] Redex - constraining what is used to fill a hole
> I'm not completely following the design goals here because it seems
> like the desire to reduce only State-Qs could be achieved by writing
> rules that reduced only State-Qs (not arbitrary states). Or are you
> saying that State-Qs are only allowed in the context? If so, then you
> could write E differently?
I don't think I can constrain the rules to only operate on State-Qs
because the *outermost* State needs to reduce, and it does not need to
be a State-Q. I think this would lead to duplicating all of the
reduction rules; once for the outermost State and once for internal
State-Qs.
It's not clear to me how I would change the definition of E to achieve this.
> you could rewrite it using define-judgment-form
This seems fairly promising - looking at the docs I don't see any
reason define-judgment-form couldn't do what I want in a
straightforward manner.
Thanks for the help,
Sam Caldwell
On Sun, Dec 13, 2015 at 5:17 PM, Robby Findler
wrote:
> I'm not completely following the design goals here because it seems
> like the desire to reduce only State-Qs could be achieved by writing
> rules that reduced only State-Qs (not arbitrary states). Or are you
> saying that State-Qs are only allowed in the context? If so, then you
> could write E differently? I think that all of this is expressible
> without using a feature like you want in Redex, but I'm not really
> getting precisely what you want so I'm hesitant to make more concrete
> suggestions.
>
> Regardless, if for some reason it is better to express your rewriting
> relation in the way that has actual premises, then you could rewrite
> it using define-judgment-form. Relations defined with
> define-judgment-form that have the mode (I O) or (O I) can be used
> with 'traces' and 'stepper' (as well as show-derivations).
>
> hth,
> Robby
>
>
> On Sat, Dec 12, 2015 at 8:21 PM, Sam Caldwell wrote:
> > Thanks for clarifying, Robby.
> >
> > I'm modeling reduction on nested states. In addition to a collection of
> > straightforward rules, there is a rule that specifies when to reduce a
> > state-inside-a-state. I can specify this using evaluation contexts, but
> in
> > order for the relation to remain deterministic I need to restrict which
> > nested-states are reduced to a particular subclass.
> >
> > I'm hoping this little model demonstrates what I'm trying to do:
> >
> > ==
> >
> > #lang racket
> >
> > (require redex)
> >
> > (define-language L
> > (State (number
> > (Event ...) ;; "incoming" events
> > (Event ...) ;; "outgoing" events
> > (State ...)))
> > (Event string)
> > ;; states with no outgoing events
> > (State-Q (number
> > (Event ...)
> > ()
> > (State ...)))
> > ;; states with no incoming or outgoing events
> > (State-I (number
> > ()
> > ()
> > (State ...)))
> > ;; Evaluation Contexts
> > (E hole
> > (number
> > ()
> > (Event ...)
> > (State-I ... E State-Q ...
> >
> > (define red
> > (reduction-relation
> >L
> >;; incoming events just increase a counter
> >(--> (number
> > (Event_0 Event_n ...)
> > (Event ...)
> > (State ...))
> > (,(add1 (term number))
> > (Event_n ...)
> > (Event ...)
> > (State ...))
> > handle)
> >;; once a State has processed all of its incoming Events, it can
> receive
> > an
> >;; outgoing Event from nested States.
> >(--> (number
> > ()
> > (Event_out ...)
> > (State-Q ...
> > (number_s
> >(Event_si ...)
> >(Event Event_so ...)
> >(State_s ...))
> > State ...))
> > (number
> > (Event Event_so ...)
> > (Event_out ...)
> > (State-Q ...
> > (number_s
> >(Event_si ...)
> >()
> >(State_s ...))
> > State ...))
> > receive)))
> >
> > #|
> > Want this to result in:
> > '((5 () () ((4 () () ()) (4 () () ()
> > |#
> > (apply-reduction-relation*
> > red
> > (term (0 ()
> > ()
> > ((1 ("hi" "hello" "ciao")
> > ("zip" "zap" "zooey")
> > ())
> >(2 ("where" "fore")
> > ("art" "thou")
> > ())
> >
> > ==
> >
> > That model allows the top-most State to process incoming Events and
> receive
> > Events from its direct children. But, I also want child States to reduce
> > using
> > the same rules. To keep my relation deterministic, I only want to step
> child
> > States that are also State-Q's. This is how I ended up trying to add a
> > shortcut like:
> >
> > [(--> (in-hole E State-Q) (in-hole E State))
> > (==> State-Q State)]
> >
> > I was able to get the behavior I want by calling apply-reduction
Re: [racket-users] Redex - constraining what is used to fill a hole
I'm not completely following the design goals here because it seems
like the desire to reduce only State-Qs could be achieved by writing
rules that reduced only State-Qs (not arbitrary states). Or are you
saying that State-Qs are only allowed in the context? If so, then you
could write E differently? I think that all of this is expressible
without using a feature like you want in Redex, but I'm not really
getting precisely what you want so I'm hesitant to make more concrete
suggestions.
Regardless, if for some reason it is better to express your rewriting
relation in the way that has actual premises, then you could rewrite
it using define-judgment-form. Relations defined with
define-judgment-form that have the mode (I O) or (O I) can be used
with 'traces' and 'stepper' (as well as show-derivations).
hth,
Robby
On Sat, Dec 12, 2015 at 8:21 PM, Sam Caldwell wrote:
> Thanks for clarifying, Robby.
>
> I'm modeling reduction on nested states. In addition to a collection of
> straightforward rules, there is a rule that specifies when to reduce a
> state-inside-a-state. I can specify this using evaluation contexts, but in
> order for the relation to remain deterministic I need to restrict which
> nested-states are reduced to a particular subclass.
>
> I'm hoping this little model demonstrates what I'm trying to do:
>
> ==
>
> #lang racket
>
> (require redex)
>
> (define-language L
> (State (number
> (Event ...) ;; "incoming" events
> (Event ...) ;; "outgoing" events
> (State ...)))
> (Event string)
> ;; states with no outgoing events
> (State-Q (number
> (Event ...)
> ()
> (State ...)))
> ;; states with no incoming or outgoing events
> (State-I (number
> ()
> ()
> (State ...)))
> ;; Evaluation Contexts
> (E hole
> (number
> ()
> (Event ...)
> (State-I ... E State-Q ...
>
> (define red
> (reduction-relation
>L
>;; incoming events just increase a counter
>(--> (number
> (Event_0 Event_n ...)
> (Event ...)
> (State ...))
> (,(add1 (term number))
> (Event_n ...)
> (Event ...)
> (State ...))
> handle)
>;; once a State has processed all of its incoming Events, it can receive
> an
>;; outgoing Event from nested States.
>(--> (number
> ()
> (Event_out ...)
> (State-Q ...
> (number_s
>(Event_si ...)
>(Event Event_so ...)
>(State_s ...))
> State ...))
> (number
> (Event Event_so ...)
> (Event_out ...)
> (State-Q ...
> (number_s
>(Event_si ...)
>()
>(State_s ...))
> State ...))
> receive)))
>
> #|
> Want this to result in:
> '((5 () () ((4 () () ()) (4 () () ()
> |#
> (apply-reduction-relation*
> red
> (term (0 ()
> ()
> ((1 ("hi" "hello" "ciao")
> ("zip" "zap" "zooey")
> ())
>(2 ("where" "fore")
> ("art" "thou")
> ())
>
> ==
>
> That model allows the top-most State to process incoming Events and receive
> Events from its direct children. But, I also want child States to reduce
> using
> the same rules. To keep my relation deterministic, I only want to step child
> States that are also State-Q's. This is how I ended up trying to add a
> shortcut like:
>
> [(--> (in-hole E State-Q) (in-hole E State))
> (==> State-Q State)]
>
> I was able to get the behavior I want by calling apply-reduction-relation
> from
> inside a rule:
>
> (--> (in-hole E State-Q)
> (in-hole E State)
> (side-condition (not (redex-match? L hole (term E
> (where (State) ,(apply-reduction-relation red (term State-Q
>
> But I can't say I felt great about doing so. (The side-condition is needed
> to
> prevent infinite looping). Is there a cleaner way to achieve the same
> result?
>
> Thanks,
> Sam Caldwell
>
>
> On Sat, Dec 12, 2015 at 11:11 AM, Robby Findler
> wrote:
>>
>> I can see why you might have expected that to work that way.
>> Unfortunately, it doesn't. The identifiers in those places in
>> shortcuts (Add2, x, and n in your examples below) are not pattern
>> positions. They are simply identifiers.
>>
>> In the code you wrote, one could change the rule's left-hand side to
>> (+ V_1 V_2) to achieve the desired effect, but maybe that doesn't work
>> in your larger model? Perhaps if you explained a little more why
>> something like that is problematic, we could be of more use.
>>
>> Meanwhile, I've pushed a fix to the bug in the error-checking that you
>> found, added some more checking, and tried to emphasize this point
>> more clearly in the documentation. The commit cbb2d88b would p
Re: [racket-users] Redex - constraining what is used to fill a hole
Thanks for clarifying, Robby.
I'm modeling reduction on nested states. In addition to a collection of
straightforward rules, there is a rule that specifies when to reduce a
state-inside-a-state. I can specify this using evaluation contexts, but in
order for the relation to remain deterministic I need to restrict which
nested-states are reduced to a particular subclass.
I'm hoping this little model demonstrates what I'm trying to do:
==
#lang racket
(require redex)
(define-language L
(State (number
(Event ...) ;; "incoming" events
(Event ...) ;; "outgoing" events
(State ...)))
(Event string)
;; states with no outgoing events
(State-Q (number
(Event ...)
()
(State ...)))
;; states with no incoming or outgoing events
(State-I (number
()
()
(State ...)))
;; Evaluation Contexts
(E hole
(number
()
(Event ...)
(State-I ... E State-Q ...
(define red
(reduction-relation
L
;; incoming events just increase a counter
(--> (number
(Event_0 Event_n ...)
(Event ...)
(State ...))
(,(add1 (term number))
(Event_n ...)
(Event ...)
(State ...))
handle)
;; once a State has processed all of its incoming Events, it can receive
an
;; outgoing Event from nested States.
(--> (number
()
(Event_out ...)
(State-Q ...
(number_s
(Event_si ...)
(Event Event_so ...)
(State_s ...))
State ...))
(number
(Event Event_so ...)
(Event_out ...)
(State-Q ...
(number_s
(Event_si ...)
()
(State_s ...))
State ...))
receive)))
#|
Want this to result in:
'((5 () () ((4 () () ()) (4 () () ()
|#
(apply-reduction-relation*
red
(term (0 ()
()
((1 ("hi" "hello" "ciao")
("zip" "zap" "zooey")
())
(2 ("where" "fore")
("art" "thou")
())
==
That model allows the top-most State to process incoming Events and receive
Events from its direct children. But, I also want child States to reduce
using
the same rules. To keep my relation deterministic, I only want to step child
States that are also State-Q's. This is how I ended up trying to add a
shortcut like:
[(--> (in-hole E State-Q) (in-hole E State))
(==> State-Q State)]
I was able to get the behavior I want by calling apply-reduction-relation
from
inside a rule:
(--> (in-hole E State-Q)
(in-hole E State)
(side-condition (not (redex-match? L hole (term E
(where (State) ,(apply-reduction-relation red (term State-Q
But I can't say I felt great about doing so. (The side-condition is needed
to
prevent infinite looping). Is there a cleaner way to achieve the same
result?
Thanks,
Sam Caldwell
On Sat, Dec 12, 2015 at 11:11 AM, Robby Findler wrote:
> I can see why you might have expected that to work that way.
> Unfortunately, it doesn't. The identifiers in those places in
> shortcuts (Add2, x, and n in your examples below) are not pattern
> positions. They are simply identifiers.
>
> In the code you wrote, one could change the rule's left-hand side to
> (+ V_1 V_2) to achieve the desired effect, but maybe that doesn't work
> in your larger model? Perhaps if you explained a little more why
> something like that is problematic, we could be of more use.
>
> Meanwhile, I've pushed a fix to the bug in the error-checking that you
> found, added some more checking, and tried to emphasize this point
> more clearly in the documentation. The commit cbb2d88b would probably
> have been the most helpful to you, but it's backwards incompatible, so
> it may need to be reverted.
>
> Robby
>
> On Fri, Dec 11, 2015 at 3:09 PM, Sam Caldwell wrote:
> > Hi,
> >
> > I'm working on a redex model where I want to constrain the shape of terms
> > used
> > to fill the hole in an evaluation context. I thought it would be fairly
> > straightforward to do so using a `with` clause in my reduction-relation,
> but
> > I've run into some difficulty, and consulting the docs [1] left me
> unsure of
> > where I went wrong.
> >
> > In the docs for `reduction-relation`, the old-arrow-name clause of
> shortcuts
> > are defined in terms of patterns and terms. However, the docs later say
> "The
> > left- and right-hand sides of a shortcut definition are identifiers, not
> > patterns and terms." I don't understand what is and is not allowed when
> > using
> > shortcuts.
> >
> > I have a small model that I think illustrates what I'm after. Say I have
> a
> > tiny addition language but for some reason I want to restrict reduction
> to
> > two-argument terms:
> >
> >
Re: [racket-users] Redex - constraining what is used to fill a hole
I can see why you might have expected that to work that way. Unfortunately, it doesn't. The identifiers in those places in shortcuts (Add2, x, and n in your examples below) are not pattern positions. They are simply identifiers. In the code you wrote, one could change the rule's left-hand side to (+ V_1 V_2) to achieve the desired effect, but maybe that doesn't work in your larger model? Perhaps if you explained a little more why something like that is problematic, we could be of more use. Meanwhile, I've pushed a fix to the bug in the error-checking that you found, added some more checking, and tried to emphasize this point more clearly in the documentation. The commit cbb2d88b would probably have been the most helpful to you, but it's backwards incompatible, so it may need to be reverted. Robby On Fri, Dec 11, 2015 at 3:09 PM, Sam Caldwell wrote: > Hi, > > I'm working on a redex model where I want to constrain the shape of terms > used > to fill the hole in an evaluation context. I thought it would be fairly > straightforward to do so using a `with` clause in my reduction-relation, but > I've run into some difficulty, and consulting the docs [1] left me unsure of > where I went wrong. > > In the docs for `reduction-relation`, the old-arrow-name clause of shortcuts > are defined in terms of patterns and terms. However, the docs later say "The > left- and right-hand sides of a shortcut definition are identifiers, not > patterns and terms." I don't understand what is and is not allowed when > using > shortcuts. > > I have a small model that I think illustrates what I'm after. Say I have a > tiny addition language but for some reason I want to restrict reduction to > two-argument terms: > > == > > #lang racket > > (require redex) > > (define-language add > (M (+ M ...) V) > (V natural) > (Add2 (+ V V)) > (E hole (+ V ... hole M ...))) > > (define red > (reduction-relation >add >(==> (+ V ...) > ,(apply + (term (V ...))) > +) >with >[(--> (in-hole E Add2) (in-hole E n)) > (==> Add2 n)])) > > == > > This does not behave as I would have expected, for example reducing > `(term (+ 1 2 (+ 3 4) 4 (+ 0 1)))` down to `15`. > > It seems like the issue is that `Add2` in the shortcut is not being used as > a > pattern. For example, if I replace `Add2` with its definition: > > [(--> (in-hole E (name x (+ V V))) (in-hole E n)) > (==> x n)] > > I get the following error message: > > free-identifier=?: contract violation > expected: identifier? > given: # > argument position: 2nd > other arguments.: > > So my question boils down to: > 1) What is/is not allowed in each position when defining a shortcut? > 2) How can I constrain what is used to fill a hole, as attempted in my > example? > > Thanks, > Sam Caldwell > > [1] > http://docs.racket-lang.org/redex/The_Redex_Reference.html#%28form._%28%28lib._redex%2Freduction-semantics..rkt%29._reduction-relation%29%29 > > -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to racket-users+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[racket-users] Redex - constraining what is used to fill a hole
Hi, I'm working on a redex model where I want to constrain the shape of terms used to fill the hole in an evaluation context. I thought it would be fairly straightforward to do so using a `with` clause in my reduction-relation, but I've run into some difficulty, and consulting the docs [1] left me unsure of where I went wrong. In the docs for `reduction-relation`, the old-arrow-name clause of shortcuts are defined in terms of patterns and terms. However, the docs later say "The left- and right-hand sides of a shortcut definition are identifiers, not patterns and terms." I don't understand what is and is not allowed when using shortcuts. I have a small model that I think illustrates what I'm after. Say I have a tiny addition language but for some reason I want to restrict reduction to two-argument terms: == #lang racket (require redex) (define-language add (M (+ M ...) V) (V natural) (Add2 (+ V V)) (E hole (+ V ... hole M ...))) (define red (reduction-relation add (==> (+ V ...) ,(apply + (term (V ...))) +) with [(--> (in-hole E Add2) (in-hole E n)) (==> Add2 n)])) == This does not behave as I would have expected, for example reducing `(term (+ 1 2 (+ 3 4) 4 (+ 0 1)))` down to `15`. It seems like the issue is that `Add2` in the shortcut is not being used as a pattern. For example, if I replace `Add2` with its definition: [(--> (in-hole E (name x (+ V V))) (in-hole E n)) (==> x n)] I get the following error message: free-identifier=?: contract violation expected: identifier? given: # argument position: 2nd other arguments.: So my question boils down to: 1) What is/is not allowed in each position when defining a shortcut? 2) How can I constrain what is used to fill a hole, as attempted in my example? Thanks, Sam Caldwell [1] http://docs.racket-lang.org/redex/The_Redex_Reference.html#%28form._%28%28lib._redex%2Freduction-semantics..rkt%29._reduction-relation%29%29 -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
