Functor Domain Versioning - Revision history

Thomas Linder Puls: category

2019-02-19T14:58:30Z

Thomas Linder Puls: released

2017-08-09T20:47:23Z

released

← Older revision		Revision as of 22:47, 9 August 2017
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	~~{{NonReleased}}~~

	It is problematic to update functor domains, if terms have been persisted in serialized form (e.g. using <vp>save</vp> to save the terms in a file).		It is problematic to update functor domains, if terms have been persisted in serialized form (e.g. using <vp>save</vp> to save the terms in a file).

Thomas Linder Puls: structure

2016-09-27T16:26:44Z

structure

← Older revision		Revision as of 18:26, 27 September 2016
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	The retired functor does not exist inside the program; the program can only see the rest of the functors, i.e. the non-retired ones.		The retired functor does not exist inside the program; the program can only see the rest of the functors, i.e. the non-retired ones.

	{{Example\|This means that you not only don't need to handle the old functor it is ~~actually~~ illegal:		{{Example\|This means that you not only don't need to handle the old functor; it is indeed illegal:
	<vip>predicates		<vip>predicates
	pred : (ppp P).		pred : (ppp P).

Thomas Linder Puls: typo

2016-09-27T16:23:20Z

typo

← Older revision		Revision as of 18:23, 27 September 2016
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	<vip>T = toTerm(ppp, "fct(7,19.5,\"something\")")		<vip>T = toTerm(ppp, "fct(7,19.5,\"something\")")
	</vip>		</vip>
	Will effectively correspond to this predicate call~~<vp>T</vp>~~		Will effectively correspond to this predicate call
	<vip>T = aaa::fct_ppp(7, 19.5, "something")		<vip>T = aaa::fct_ppp(7, 19.5, "something")
	</vip>		</vip>

Thomas Linder Puls: elaborate

2016-09-27T16:20:56Z

elaborate

Show changes

Thomas Linder Puls: initial

2016-09-27T15:22:00Z

initial

New page

{{Template:NonReleased}}

It is problematic to update functor domains, if terms have been persisted in serialized form. Because new programs cannot deal with old serializations.

The attributes <vp>default/1</vp> and <vp>retiredFunctor/1</vp> can help dealing with this problem.

== Default values ==

The last arguments of a functor can have default values:

<vip>domains
ppp =
fct(
integer A,
real B,
ddd C,
integer* New [default([])],
real New2 [default(0)]
).</vip>

The default attribute does not change anything within the program; it only affects the deserialization. If during deserialization we meet the closing parenthesis too soon we supply default values for the remaining arguments.

Notice that this will only work for text deserialization.

== Retired functors ==

Functor alternatives can be retired.

<vip>domains
ppp =
fct(integer A, real B, ddd C) [retiredFunctor(aaa::fct_ppp)];
fct2(integer A, ddd C, integer* New).</vip>

<vp>aaa::fct_ppp</vp> must be a predicate with this type (it can be an anonymous predicate):

<vip>predicates
fct_ppp : (integer A, real B, ddd C) -> ppp NewValue.</vip>

I.e. it takes the arguments of the old functor and returns a value in the functor domain.

In the program <vp>fct</vp> is does not exist at all, it is retired. However, in the deserialization <vp>fct</vp> terms can still be handled: The arguments are parsed according to the types, and then the value is created by invoking <vp>aaa::fct_ppp</vp>.

This method will also work for binary serializations, provided:

* The old domain had more than one alternative (so there are functor numbers in the serialization)
* New alternatives are added last (to retain functor numbers)

(It is however not recommend using binary serialization for inter-session persistence).
[[Category:Tutorials|{{PAGENAME}}]]

← Older revision		Revision as of 16:58, 19 February 2019
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	(It is however not recommend using binary serialization for inter-session persistence).		(It is however not recommend using binary serialization for inter-session persistence).

	[[Category:~~Tutorials~~\|{{PAGENAME}}]]		[[Category:Data types and handling\|{{PAGENAME}}]]