List::map and list:forall - shall I forget them?

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Ferenc Nagy
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List::map and list:forall - shall I forget them?

Unread post by Ferenc Nagy » 17 Sep 2015 7:36

The new VIP introduced

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foreach and [ || ]
structures.
The

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findall, list::map and list:forall
are earlier language features.
Shall I forget them and use

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foreach and [ || ]
in the future?
TIA, Regards,
Frank Nagy

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Thomas Linder Puls
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Unread post by Thomas Linder Puls » 17 Sep 2015 18:16

You should forget findall, but the other ones may still be useful/preferred in some contexts.
Regards Thomas Linder Puls
PDC

Peter Muraya
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Unread post by Peter Muraya » 18 Sep 2015 6:20

Frank,
My simple understanding is that the list comprehension, [||], replaced findall.

list::map and list::forall are additions that if they commonly appear in your code they are neater to use (and understand) than the equivalent coded using foreach. See the following examples....
...using list::map

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.... Z=list::map(Xs, Y), ...
... and not using list::map

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... C=varM:new(), foreach X in Xs do      C:value:=list::append(C:value, Y(X)) end foreach, Z=C:value, ...
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Thomas Linder Puls
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Unread post by Thomas Linder Puls » 18 Sep 2015 8:00

It would be more natural to use list comprehension to map (and foreach to do forall):

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    % map     Ma = map(L, f),     Mb = [ f(X) || X in L],     % forall     forall(L, p),     foreach Y in L do         p(Y)     end foreach
If the function you map with and the predicate you "forall" with are existing as named entities in your code then the use of the map and forall predcates are quite simple and easy to read.

But if the code is more complex and you for example need to use anonymous predicates then the list comprehension and foreach versions may be prefarable.

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        Z = q(...),         % map         Ma =             map(L,                 { (X) = f(V, Z) :-                     V1 = g(Z, 12),                     V2 = h(V1)                 }),         Mb =             [ f(V, Z) ||                 X in L,                 V1 = g(Z, 12),                 V2 = h(V1)             ],         % forall         forall(L,             { (Y) :-                 V1 = a(Y, Z),                 V2 = b(Y, V1),                 p(V2)             }),         foreach Y in L do                 V1 = a(Y, Z),                 V2 = b(Y, V1),                 p(V2)         end foreach.
Regards Thomas Linder Puls
PDC

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