将谓词应用于列表元素的 Prolog 映射过程 [英] Prolog map procedure that applies predicate to list elements

问题描述

你如何编写一个 Prolog 过程 map(List, PredName, Result) 将谓词 PredName(Arg, Res) 应用到 List 的元素，并返回列表中的结果Result?

How do you write a Prolog procedure map(List, PredName, Result) that applies the predicate PredName(Arg, Res) to the elements of List, and returns the result in the list Result?

例如:

test(N,R) :- R is N*N.

?- map([3,5,-2], test, L).
L = [9,25,4] ;
no

推荐答案

这通常称为 maplist/3 并且是 序言序言.注意不同的参数顺序！

This is usually called maplist/3 and is part of the Prolog prologue. Note the different argument order!

:- meta_predicate maplist(2, ?, ?).

maplist(_C_2, [], []).
maplist( C_2, [X|Xs], [Y|Ys]) :-
   call(C_2, X, Y),
   maplist( C_2, Xs, Ys).

不同的参数顺序允许您轻松嵌套多个 maplist 目标.

The different argument order permits you to easily nest several maplist-goals.

?- maplist(maplist(test),[[1,2],[3,4]],Rss).
Rss = [[1,4],[9,16]].

maplist 有不同的参数，对应于 以下是函数式语言中的结构，但要求所有列表的长度相同.请注意，Prolog 没有 zip/zipWith 和 unzip 之间的不对称性.目标 maplist(C_3, Xs, Ys, Zs) 包含两者，甚至提供更通用的用途.

maplist comes in different arities and corresponds to the following constructs in functional languages, but requires that all lists are of same length. Note that Prolog does not have the asymmetry between zip/zipWith and unzip. A goal maplist(C_3, Xs, Ys, Zs) subsumes both and even offers more general uses.

• maplist/2 对应于 all
• maplist/3 对应于 map
• maplist/4 对应于 zipWith 但也对应于 unzip
• maplist/5 对应于 zipWith3 和 unzip3
• ...

• maplist/2 corresponds to all
• maplist/3 corresponds to map
• maplist/4 corresponds to zipWith but also unzip
• maplist/5 corresponds to zipWith3 and unzip3
• ...

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