如何解决Prolog中未定义的过程错误？

Question

我在一台提供的计算机上编写了这段代码：

factor_in_inches(Unit, Scale) :- scale_of(Unit, Scale, inch).


scale_factor(Unit1, Unit2, Factor) :- scale_of(Unit2, Factor, Unit1).

%PartI
scales(BigUnit, Scale, LittleUnit) :-
    scale(BigUnit, Scale, LittleUnit);
    scale(LittleUnit, Scale1, BigUnit),
    Scale is 1/Scale1.


%check if input follow base or reverse predicate
scale_of(BigUnit, Scale, LittleUnit) :- 
    scales(BigUnit, Scale, LittleUnit);
    scales(BigUnit, Scale1, LittleUnit1), 
    scale_of(LittleUnit1, Scale2, LittleUnit),
    Scale is Scale1 * Scale2.

%Checks if Unit1 * Quantity1 = Unit2 * Quantity2
convert(Unit1, Quantity1, Unit2, Quantity2) :-
    factor_in_inches(Unit1, Scale1),
    factor_in_inches(Unit2, Scale2),
    Scale1 is round(Scale2 * Quantity2 / Quantity1).

我正在尝试为我的家庭作业运行一个小的测试用例，如下所示：

:- begin_tests(imperial_part1).

  test(factor_in_inches) :- factor_in_inches(inch,  1.0).
  test(factor_in_inches) :- factor_in_inches(foot, 12.0).
  test(factor_in_inches) :- factor_in_inches(rod, 198.0).

:- end_tests(imperial_part1).

但是，每当我运行测试时，我都会收到以下错误：

ERROR: /Users/brianpattison/Desktop/Semester_2/Progamming_Languages/Prolog/SWI-Prolog.app/Contents/MacOS/imperial_hw.pl:67:
    test factor_in_inches: received error: plunit_imperial_part1:'unit body'/2: Undefined procedure: plunit_imperial_part1:factor_in_inches/2
  However, there are definitions for:
        factor_in_inches/2
ERROR: /Users/brianpattison/Desktop/Semester_2/Progamming_Languages/Prolog/SWI-Prolog.app/Contents/MacOS/imperial_hw.pl:68:
    test factor_in_inches: received error: plunit_imperial_part1:'unit body'/2: Undefined procedure: plunit_imperial_part1:factor_in_inches/2
  However, there are definitions for:
        factor_in_inches/2
ERROR: /Users/brianpattison/Desktop/Semester_2/Progamming_Languages/Prolog/SWI-Prolog.app/Contents/MacOS/imperial_hw.pl:69:
    test factor_in_inches: received error: plunit_imperial_part1:'unit body'/2: Undefined procedure: plunit_imperial_part1:factor_in_inches/2
  However, there are definitions for:
        factor_in_inches/2

我已经尝试了很多次来解决这个问题，但我无法解决。

有什么建议吗？

Answer 1

plunit工具期望您想要测试的代码封装在一个模块中。您的代码中还缺少一个谓词，scale/3。相反，尝试：

:- module(foo, []).

% your code here

:- begin_tests(imperial_part1).

% your tests here

:- end_tests(imperial_part1).

然后：

?- [foo], run_tests.

您将得到(由于缺少谓词)：

ERROR: .../foo.pl:30:
    test factor_in_inches: received error: foo:scales/3: Unknown procedure: foo:scale/3
  However, there are definitions for:
        foo:scales/3
ERROR: .../foo.pl:31:
    test factor_in_inches: received error: foo:scales/3: Unknown procedure: foo:scale/3
  However, there are definitions for:
        foo:scales/3
ERROR: .../foo.pl:32:
    test factor_in_inches: received error: foo:scales/3: Unknown procedure: foo:scale/3
  However, there are definitions for:
        foo:scales/3

添加缺少的谓词，您的测试就应该运行。