[curry] Re: Specifying default rules: Why and how?

From: Jeffrey Brown <jeffbrown.the_at_gmail.com>
Date: Thu, 22 Nov 2018 00:17:01 -0500

I've almost got currypp working! It's installed, but reports
"pakcs-frontend: /usr/lib/pakcs/lib/.curry/Prelude.uacy: openFile:
permission denied (Permission denied)
ERROR: i/o error: ERROR: user error: Illegal source program". I put more
details on StackOverflow[1].

Thank you both!

[1]
https://stackoverflow.com/questions/53357361/specifying-default-rules-in-th=
e-curry-language-why-and-how/53367863#comment93722810_53367863

On Mon, Nov 19, 2018 at 12:07 PM Michael Hanus <mh_at_informatik.uni-kiel.de>
wrote:

> Hi Jeff,
>
> maybe at some tome in the future, default rules, set functions etc
> will become part of the syntax of Curry and, thus, processed by
> the standard parser.
>
> In the current "development" state, they are processed and
> implemented by the Curry preprocessor. This provides more flexibility
> for us (to play with different implementations) but allows
> also unintended uses. As a compromise, you might use CurryCheck,
> a property-based test tool which also perform some static code tests.
> For instance, running CurryCheck on your program generates the
> the message
>
> Analyzing module 'Test'...
>
> =========================
==========================
==========================
====
> STATIC ERRORS IN PROGRAMS:
> 'Test' uses default rules or det. operations but not the preprocessor!
> Hint: insert line: {-# OPTIONS_CYMAKE -F --pgmF=currypp #-}
>
> =========================
==========================
==========================
====
>
> Hence, you see what is missing...
>
> CurryCheck can easily be installed by Curry's package manager:
>
> > cypm update && cypm install currycheck
>
> Best regards,
>
> Michael
>
> On 11/19/18 4:49 AM, Jeffrey Brown wrote:
> > Awesome! Thanks, Sergio!
> >
> > On Sun, Nov 18, 2018 at 10:24 PM <h7sa_at_pdx.edu <mailto:h7sa_at_pdx.edu>>
> wrote:
> >
> > Hi Jeff
> >
> > Answered on Stackoverflow. Good question. The tutorial should be
> > clear about using the preprocessor. Sorry.
> >
> > Sergio
> >
> > On Sun, 18 Nov 2018, at 19:50, Jeffrey Brown
> > <jeffbrown.the_at_gmail.com <mailto:jeffbrown.the_at_gmail.com>> wrote:
> >
> > > I posted this question on Stackoverflow[1] yesterday and haven't
> > received
> > > any answers yet. I've duplicated the question below, but an
> > answer posted
> > > to StackOverflow would be more useful to future students, if
> > you're so
> > > inclined.
> > >
> > > Thanks!
> > >
> > > ---
> > >
> > > In section 3.5.6 of the Curry tutorial (pdf)
> > >
> > <https://www.informatik.uni-kiel.de/~curry/tutorial/tutorial.pdf>,
> > we are
> > > advised to use default rules to "regain control after a failed
> > search". The
> > > following example is given. (For clarity I have added a type
> > signature and
> > > curried the input.)
> > >
> > > lookup :: k -> [(k,v)] -> Maybe v
> > > lookup key (_++[(key,value)]++_ ) = Just value
> > > lookup’default _ _ = Nothing
> > >
> > > I can't get that to compile unless I replace the ’ with =
a '. Once
> > I do, it
> > > behaves like this:
> > >
> > > test> test.lookup 1 [(2,3)]
> > > *** No value found!
> > >
> > > Question 1: What is the default declaration for?
> > >
> > > Why would you need to specify that a particular clause is the
> > default one?
> > > Won't it be arrived at one way or another, once the others fail?
> > > Question 2: How is it written? Should it be written at all?
> > >
> > > If instead I drop the string 'default:
> > >
> > > lookup :: k -> [(k,v)] -> Maybe v
> > > lookup key (_++[(key,value)]++_ ) = Just value
> > > lookup _ _ = Nothing
> > >
> > > it behaves as intended:
> > >
> > > test> test.lookup 1 [(2,3)]
> > > Nothing
> > > test>
> > >
> > > Has the 'default syntax changed since the tutorial was written?
> > Has it been
> > > removed altogether?
> > > [1]
> > >
> >
> https://stackoverflow.com/questions/53357361/specifying-default-rules-in-=
the-curry-language-why-and-how
> > >
> > > --
> > > Jeff Brown | Jeffrey Benjamin Brown
> > > Website <https://msu.edu/~brown202/> | Facebook
> > > <https://www.facebook.com/mejeff.younotjeff> | LinkedIn
> > > <https://www.linkedin.com/in/jeffreybenjaminbrown>(spammy, so I
> > often miss
> > > messages here) | Github <
> https://github.com/jeffreybenjaminbrown>
> >
> > > _______________________________________________
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> > >
> >
> https://lists.rwth-aachen.de/postorius/lists/curry.lists.rwth-aachen.de
> >
> >
> >
> > --
> > Jeff Brown | Jeffrey Benjamin Brown
> > Website <https://msu.edu/~brown202/> | Facebook
> > <https://www.facebook.com/mejeff.younotjeff> | LinkedIn
> > <https://www.linkedin.com/in/jeffreybenjaminbrown>(spammy, so I often
> > miss messages here) | Github
> > <https://github.com/jeffreybenjaminbrown>
>
>

--
Jeff Brown | Jeffrey Benjamin Brown
Website <https://msu.edu/~brown202/> | Facebook
<https://www.facebook.com/mejeff.younotjeff> | LinkedIn
<https://www.linkedin.com/in/jeffreybenjaminbrown>(spammy, so I often miss
messages here) | Github <https://github.com/jeffreybenjaminbrown>



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Received on Fri Nov 23 2018 - 09:37:25 CET

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