CLPB 的不良特性 [英] Undesirable properties of CLPB

问题描述

library(clpb) 目前在 SICStus(原始版本)和 SWI(通过 mat)中可用.让我很快进入本质:

?- X = 1+1, sat(X), X = 1+1.X = 1+1.?- sat(X)，X = 1+1.错误的.

所以这是一个类似的问题，因为它存在于library(clpfd)的默认状态.

遇到这种情况怎么办?

更新:在mat的library(clpfd)中，现在有用于此目的的函子#/1.理想情况下，加上运算符声明 op(150,fx,#)，我们现在可以这样写:

?- X = 1+1, #X #= Y.错误:类型错误:应为整数"，找到1+1"(复合)

为了确保完整的代数属性，必须声明:

:- set_prolog_flag(clpfd_monotonic, true).

现在，不明确的变量(因此，只能是整数或表达式)会产生实例化错误:

?- 1 + 1 #= Y.错误:参数未充分实例化?- 1 + 1 #= #Y.Y = 2.

解决方案

<块引用>

遇到这种情况怎么办?

同时，library(clpb) 也确保了类似于 library(clpz)/library(clfd) 的单调性.在这种执行模式下，显式变量必须用 (v)/1 修饰.

?- current_prolog_flag(clpb_monotonic,B).B = 错误.% 默认?- 坐(X).X = 1.?- set_prolog_flag(clpb_monotonic,true).真的.?- 坐(X).错误:参数未充分实例化?- sat(v(X)).X = 1.

在 Scryer 中，说:

?- use_module(library(clpb)).真的.?-断言(clpb:单调).真的.?- 坐(X).捕获:错误(实例化错误，实例化错误(未知(_67)，1))?- sat(v(X)).X = 1;错误的.

library(clpb) is currently available in SICStus (original version), and SWI (by mat). Let me come to the essence quite rapidly:

?- X = 1+1, sat(X), X = 1+1.
X = 1+1.

?-          sat(X), X = 1+1.
false.

So this is a similar problem as it exists in the default state of library(clpfd).

What to do in such a situation?

Update: In library(clpfd) of mat, there is now the functor # /1 for this purpose. Ideally, accompanied with an operator declaration op(150,fx,#), we now can write:

?- X = 1+1, #X #= Y.
ERROR: Type error: `integer' expected, found `1+1' (a compound)

To ensure full algebraic properties one has to declare:

:- set_prolog_flag(clpfd_monotonic, true).

Now, variables that are left ambiguous (thus, being either integers only, or expressions) produce instantiation errors:

?-  1 + 1 #= Y.
ERROR: Arguments are not sufficiently instantiated
?- 1 + 1 #= #Y.
Y = 2.

解决方案

What to do in such a situation?

In the meantime, also library(clpb) ensures monotonicity similar to library(clpz)/library(clfd). Within this execution mode, explicit variables have to be decorated with (v)/1.

?- current_prolog_flag(clpb_monotonic,B).
B = false.                             % the default

?- sat(X).
X = 1.

?- set_prolog_flag(clpb_monotonic,true).
true.

?- sat(X).
ERROR: Arguments are not sufficiently instantiated

?- sat(v(X)).
X = 1.

In Scryer, say:

?- use_module(library(clpb)).
   true.
?- asserta(clpb:monotonic).
   true.
?- sat(X).
caught: error(instantiation_error,instantiation_error(unknown(_67),1))
?- sat(v(X)).
   X = 1
;  false.

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