Question

我开始学习prolog，这是我被困的地方，我有一个演绎db如下，

employee(smith, accounting, 30000).
employee(jones, accounting, 50000).
employee(mary, accounting, 40000).
employee(helen, payroll, 20000).
employee(mike, payroll, 10000).
department(accounting, jones, 3).
department(payroll, helen, 2).

我需要一个Prolog谓词manager_higherSalary_biggerDept来查找薪水超过40000且员工人数超过特定部门的员工的姓名。

例如，要查找大小超过工资单的部门经理一年超过40000，查询：

?- manager_higherSalary_biggerDept(M, 40000, payroll).

应该给：M =琼斯; 无

Answer 1

这很简单（未经测试）：

manager_higherSalary_biggerDept(Name, SalaryThreshold, DeptName) :-
    employee(Name, _, Salary),
    Salary > SalaryThreshold,
    department(DeptName, _, DeptThreshold),
    department(_, Name, Dept),
    Dept > DeptThreshold.

Answer 2

Prolog是一种声明性语言。这意味着您描述问题的解决方案并让其推理引擎完成工作。所以......

manager_of_bigger_department_with_higher_salary( M , S , D ) :- %
  department(D,_,DS) ,                                          % get the size of the targer department
  manages_department_larger_than(M,DS) ,                        % find the manager of a larger department
  has_higher_salary_than(M,S)                                   % who has a salary higher than the specified threshold
  .                                                             % 

manages_department_larger_than( M , D , T ) :-
  department(D,M,S) ,
  S > T
  .

has_salary_higher_than( E , T ) :-
  employee(E,_,S) ,
  S > T
  .

使用Prolog进行演绎数据库

2 个答案: