Author:
http://www.ruby-cn.org/
2004/11/23
In a Martin Fowler on a closed package (http://martinfowler.com/bliki/closures.html, Chinese: http://www.ruby-cn.org/articles/closures.html), In an example, it is mainly written in the Ruby language. Later, there have been many versions of other languages. This article adds the various versions to make you read more.
Ruby
Excerpt from the original http://martinfowler.com/bliki/closures.html1.
DEF Managers (EMPS)
Return Emps.select {| e | e.ismanager}
end
2.
DEF Highpaid (EMPS)
Threshold = 150
Return Emps.select {| e | e.salary> threshold}
end
3.
Def Paidmore (Amount)
Return proc.new {| e | e.salary> Amount}
end
4.
HIGHPAID = PAIDMORE (150)
John = EMPLOYE.NEW
John.salary = 200
HIGHPAID.CALL (John)
2.c # 2.0
Excerpted from: http://joe.truemesh.com/blog//000390.html
1.
Public List
Return Emps.FindAll (delegate (Employee E) {
Return E.Ismanager;
}
}
2.
Public List
INT thRESHOLD = 150;
Return Emps.FindAll (delegate (Employee E) {
Return E.SALARY> thRESHOLD;
});
}
3.
Public Predicate
Return delegate (Employee e) {
Return E.SALARY> AMOUNT;
}
}
4.
Predicate
Employee john = new employee ();
John.salary = 200;
Console.writeline (HighPaid (John));
3.python
Excerpt from: http://ivan.truemesh.com/archives/000392.html
Direct Lambda functions
1.
Def Managers (Emps): Return Filter (Lambda E: E.ismanager, EMPS)
2.
Def Highpaid (Emps): Threshold = 150 Return Filter (Lambda E: E.SALARY> Threshold, EMPS)
3.
Def Paidmore (Amount): Return Lambda E: E.SALARY> Amount
4.
HIGHPAID = PAIDMORE (150) John = Employee () John.salary = 200PRINT HighPAID (John) Another way, with list included (List comprehensions)
1.
Def Managers (EMPS): Return [e for e in Emps if E.ismanager]
2.
DEF HIGHPAID (EMPS): Threshold = 150 Return [e for e in Emps if e.salary> threshold]
Chris Reed provides another way to avoid using lambda:
DEF PAIDMORE (AMOUNT):
DEF PAIDMORECHECK (E):
Return E.SAlary> Amount
Return PaiDmoreCheck
4.java
Excerpted from: http://joe.truemesh.com/blog//000390.html
JDK 1.5 support
Private class FindhightEmployees extends algorithms {
ConsTRAINT HIGHPAIDEMPLOYEE;
Public FindHighPaideMployESS (construint constraint) {
THIS.HIGHPAIDEMPLOYEEEEEE = ConsTRAINT;
}
Public Object Call (Object O) {
List Emps = (List) O;
Return Findall (EMPS, HIGHPAIDEMPLOYEE);
}
}
Private class paidmore usments constraint {
Private int sale;
Public paidmore (int sales) {
THIS.SALARY = SALARY;
}
Public Boolean Test (Object O) {
Return (Integer O) .intValue ()> SALARY;
}
}
Closure HighPaidFinder = New FindhightEmployees (New Paidmore (150));
List hightpaidemployees = highpaidfinder.call (myemployees);
