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From: Sebastian Fischer <sebf_at_informatik.uni-kiel.de>

Date: Sat, 19 Feb 2011 13:02:03 +0900

Hello,

I thought that the difference between the expressions (=:= e) and (\x ->

x =:= e) is only observable in the context of encapsulated search but just

noticed that it is observable in ordinary Curry programs too (using both

PAKCS and MCC).

"Each right section (op expr) is transformed into the lambda abstraction

(\x->(op) x expr) where x is a new variable." [Report on Curry, page 82]

Therefore, a difference between the following two predicates should not be

observable:

partial = (=:= coin)

lambda = (\x -> x =:= coin)

The following function computes two solutions to a given predicate:

twoSols p | p x & p y = (x,y)

where x,y free

It can be used to observe a difference between 'partial' and 'lambda':

cyi> twoSols partial

(0,0)

More solutions? [Y(es)/n(o)/a(ll)]

(1,1)

cyi> twoSols lambda

(0,0)

More solutions? [Y(es)/n(o)/a(ll)]

(0,1)

More solutions? [Y(es)/n(o)/a(ll)]

(1,0)

More solutions? [Y(es)/n(o)/a(ll)]

(1,1)

It seems related to the 'fcoin' example of the Toy community [1] which lead

to removing the mention of eta-expansion from the Curry report. Is it a

known issue that neither PAKCS nor MCC conform to the Curry report regarding

right sections?

[1]: http://www.informatik.uni-kiel.de/~curry/listarchive/0499.html

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curry_at_lists.RWTH-Aachen.DE

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Received on Sa Feb 19 2011 - 18:57:53 CET

Date: Sat, 19 Feb 2011 13:02:03 +0900

Hello,

I thought that the difference between the expressions (=:= e) and (\x ->

x =:= e) is only observable in the context of encapsulated search but just

noticed that it is observable in ordinary Curry programs too (using both

PAKCS and MCC).

"Each right section (op expr) is transformed into the lambda abstraction

(\x->(op) x expr) where x is a new variable." [Report on Curry, page 82]

Therefore, a difference between the following two predicates should not be

observable:

partial = (=:= coin)

lambda = (\x -> x =:= coin)

The following function computes two solutions to a given predicate:

twoSols p | p x & p y = (x,y)

where x,y free

It can be used to observe a difference between 'partial' and 'lambda':

cyi> twoSols partial

(0,0)

More solutions? [Y(es)/n(o)/a(ll)]

(1,1)

cyi> twoSols lambda

(0,0)

More solutions? [Y(es)/n(o)/a(ll)]

(0,1)

More solutions? [Y(es)/n(o)/a(ll)]

(1,0)

More solutions? [Y(es)/n(o)/a(ll)]

(1,1)

It seems related to the 'fcoin' example of the Toy community [1] which lead

to removing the mention of eta-expansion from the Curry report. Is it a

known issue that neither PAKCS nor MCC conform to the Curry report regarding

right sections?

[1]: http://www.informatik.uni-kiel.de/~curry/listarchive/0499.html

_______________________________________________

curry mailing list

curry_at_lists.RWTH-Aachen.DE

http://MailMan.RWTH-Aachen.DE/mailman/listinfo/curry

Received on Sa Feb 19 2011 - 18:57:53 CET

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