evaluation

问题 I have this class hierarchy StudentClass .java public class StudentClass { private List<Student> studentList; public List<Student> getStudentList() { return studentList; } public void setStudentList(List<Student> studentList) { this.studentList = studentList; } } Student.java public class Student { private Child child; private int studAge; public Student(Child child, int studAge) { this.child = child; this.studAge = studAge; } public Child getChild() { return child; } public void setChild

问题 If I define λ> data Bar = Bar Int deriving Show λ> data Foo = Foo Bar deriving Show and λ> let foo = trace "foo" Foo (trace "bar" Bar 100) λ> let two = trace "two" 2 λ> let g (Foo x) y = y then I think I understand why I get λ> g foo two foo two 2 But if I then repeat this, I get λ> g foo two two 2 and I don't understand why foo appears not to have been evaluated for the second invocation of g , especially since it is clearly not (yet) somehow already available, as I can verify with λ> foo

问题 I'm trying to learn LISP and was going through a code example where something similar to the following code is used: (list 'quote 5) This evaluates to '5 in the REPL. I expected it to evaluate to ('5) or (quote 5) I'm trying this out in the CLISP REPL. Any help would be appreciated. 回答1: The read-evaluate-print loop first reads, then evaluates 'quote is read as "the symbol whose name is QUOTE" 5 is read as "the number 5" So (list 'quote 5) is evaluated as "make a list whose first element is

问题 I'm trying to learn LISP and was going through a code example where something similar to the following code is used: (list 'quote 5) This evaluates to '5 in the REPL. I expected it to evaluate to ('5) or (quote 5) I'm trying this out in the CLISP REPL. Any help would be appreciated. 回答1: The read-evaluate-print loop first reads, then evaluates 'quote is read as "the symbol whose name is QUOTE" 5 is read as "the number 5" So (list 'quote 5) is evaluated as "make a list whose first element is

问题 I'm using Rapidminer to do an analysis. I used cross-validation on several models to get the best working model. Now I want to use this model to test on a separate testset that I made using Split Data to estimate the performance. How do I use the test set? As far as I can tell, all the validation modules use the training set that the model was made on. Which performance measure can I use that takes in a model and my test set? 回答1: Use the "Apply Model" operator with your model as the first

问题 I'm using Rapidminer to do an analysis. I used cross-validation on several models to get the best working model. Now I want to use this model to test on a separate testset that I made using Split Data to estimate the performance. How do I use the test set? As far as I can tell, all the validation modules use the training set that the model was made on. Which performance measure can I use that takes in a model and my test set? 回答1: Use the "Apply Model" operator with your model as the first

问题 The question should be interpreted from a general point of view and not targeted solely at web apps or desktop apps. I have been looking around to find a simple and easy way of creating interactive prototypes for web applications. I'd like to use a technique that allows simple UI creation and especially UI recreation and modification in further iterations. Filling the UI with mockup data should be very simple. The technique may require a simple form of programming, e.g. to specify a drag and

问题 The question should be interpreted from a general point of view and not targeted solely at web apps or desktop apps. I have been looking around to find a simple and easy way of creating interactive prototypes for web applications. I'd like to use a technique that allows simple UI creation and especially UI recreation and modification in further iterations. Filling the UI with mockup data should be very simple. The technique may require a simple form of programming, e.g. to specify a drag and

问题 Consider the following: class MyClass { private $var1 = "apple"; private $var2 = "orange"; } $obj = new MyClass(); if($obj) { // do this } else { // do that } PHP evaluates my object to true because it has member variables. Can this logic be overridden somehow? In other words, can I have control over what an object of my class will evaluate to when treated as a boolean? 回答1: PHP evaluates my object to true because it has member variables. This is incorrect. PHP actually evaluates $obj as true

问题 I'm about to start a new project which should have a rather large database. The number of tables will not be large (<15), majority of data (99%) will be contained in one big table, which is almost insert/read only (no updates). The estimated amount of data in that one table is going to grow at 500.000 records a day , and we should keep at least 1 year of them to be able to do various reports. There needs to be (read-only) replicated database as a backup/failover, and maybe for offloading