list - 以 'raw' ./2 格式显示列表

Question

是否可以以 ./2 格式显示 Prolog 列表，例如

对于列表:

| ?- L=[a,b,c].
L = [a,b,c] ? 
yes

有没有办法显示:

L = .(a, .(b, .(c, []))).

Answer 1

通常，write_canonical(List)或 ?- write_term(List, [quoted(true), ignore_ops(true)]) ，正如评论中指出的那样。由于 SWI-Prolog 决定 do things differently ，这还不够好:

?- write_canonical([a]).
[a]
true.

?- write_term([a], [quoted(true), ignore_ops(true)]).
[a]
true.

?- write_term([a], [dotlists(true)]).
.(a,[])
true.

见 documentation on write_term/2 ，注意选项 brace_terms(Bool)和 dotlists(Bool) .但要注意:如果您正常启动 SWI-Prolog 7， ./2不再是列表仿函数了!

?- L = .(a, []).
ERROR: Type error: `dict' expected, found `a' (an atom) % WHAT?

?- L = '[|]'(a, []).
L = [a].

如果您以 swipl --traditional 开头，事情恢复正常，有点:

$ swipl --traditional
Welcome to SWI-Prolog (Multi-threaded, 64 bits, Version 7.3.4-32-g9311e51)
Copyright (c) 1990-2015 University of Amsterdam, VU Amsterdam
SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to redistribute it under certain conditions.
Please visit http://www.swi-prolog.org for details.

For help, use ?- help(Topic). or ?- apropos(Word).

?- L = .(a, []).
L = [a].

您仍然无法使用 write_canonical(List)或 write_term(List, [quoted(true), ignore_ops(true)]) .

阅读 SWI-Prolog 文档的链接部分以了解详细信息和基本原理。作为建议，如果您决定使用 SWI-Prolog，请坚持使用默认设置的 SWI-Prolog 7，并且只使用 write_term(List, [dotlists(true)])如果您需要与另一个 Prolog 实现进行通信。通常的列表符号， [a, b, ...]在大多数常规情况下应该足够好。