xsb "No procedure usermod" 当谓词已经定义时

Question

所以在我的文件中有

:- use_module(standard, datime/1).

today(Y, M, D) :-
    datime(datime(Y, M, D, _, _, _).

运行这个直接在命令行给出

XSB Version 3.6. (Gazpatcho) of April 22, 2015
[x86-pc-windows; mode: optimal; engine: slg-wam; scheduling: local]
[Build date: 2015-04-22]

| ?- use_module(standard, datime/1).

yes
| ?- datime(datime(Y, M, D, _, _, _)).

Y = 2016
M = 5
D = 17

yes

但是加载文件本身和运行函数给出了一个错误

| ?- [utils].
[Compiling .\utils]
[utils compiled, cpu time used: 0.0780 seconds]
[utils loaded]

yes
| ?- today(Y, M, D).
++Error[XSB/Runtime/P]: [Existence (No procedure usermod : today / 3 exists)] []
Forward Continuation...
... machine:xsb_backtrace/1  From C:\Program Files (x86)\XSB\syslib\machine.xwam
... loader:load_pred1/1  From C:\Program Files (x86)\XSB\syslib\loader.xwam
... loader:load_pred0/1  From C:\Program Files (x86)\XSB\syslib\loader.xwam
... loader:load_pred/1  From C:\Program Files (x86)\XSB\syslib\loader.xwam
... x_interp:_$call/1  From C:\Program Files (x86)\XSB\syslib\x_interp.xwam
... x_interp:call_query/1  From C:\Program Files (x86)\XSB\syslib\x_interp.xwam
... standard:call/1  From C:\Program Files (x86)\XSB\syslib\standard.xwam
... standard:catch/3  From C:\Program Files (x86)\XSB\syslib\standard.xwam
... x_interp:interpreter/0  From C:\Program Files (x86)\XSB\syslib\x_interp.xwam
... loader:ll_code_call/3  From C:\Program Files (x86)\XSB\syslib\loader.xwam
... standard:call/1  From C:\Program Files (x86)\XSB\syslib\standard.xwam
... standard:catch/3  From C:\Program Files (x86)\XSB\syslib\standard.xwam

知道为什么会这样以及如何解决这个问题吗？文件中的其他谓词也会发生这种情况。

Answer 1

您的代码有 3 个问题：

您的 today/3 声明缺少结尾 )、
today/3 未导出
use_module/2 需要一个符号列表作为第二个参数，或者使用 import sym from mod.

如果您将 utils.P 文件定义如下

:- import datime/1 from standard.
:- export today/3.
today(Y, M, D) :- datime(datime(Y, M, D, _, _, _)).

您可以通过以下任一方式使用它：

直接导入谓词：

| ?- import today/3 from utils.

yes
| ?- today(Y,M,D).

Y = 2016
M = 5
D = 18

使用限定名称使用 :

| ?- utils:today(Y,M,D).

Y = 2016
M = 5
D = 18

直接加载模块

| ?- [utils].
[utils loaded]

| ?- today(Y,M,D).

Y = 2016
M = 5
D = 18

xsb "No procedure usermod" 当谓词已经定义时

xsb "No procedure usermod" when predicate is already defined

prolog

xsb