enumerator

I'm subclassing Enumerator like this: class CuadraticPrimeGenerator < Enumerator def initialize(a=1,b=49) super do |y| x = 1 loop do y << x**2 + a*x + b x += 1 end end end end However... > CuadraticPrimeGenerator.new(1,49) 0027.rb:41:in `initialize': 49 is not a symbol (TypeError) from 0027.rb:41:in `initialize' from 0027.rb:48:in `new' from 0027.rb:48:in `<main>' Thoughts? What about: class CuadraticPrimeGenerator < Enumerator def initialize(a=1,b=49) super() do |y| count, x = 0, 1 loop { y.yield(x**2 + a*x + b) } end end end 来源： https://stackoverflow.com/questions/16016995/argumenterror-in

This is a spin-off question based on Eric Lippert's answer on this question . I would like to know why the C# language is designed not being able to detect the correct interface member in the following specific case. I am not looking on feedback whether designing a class this way is considered best practice. class Turtle { } class Giraffe { } class Ark : IEnumerable<Turtle>, IEnumerable<Giraffe> { public IEnumerator<Turtle> GetEnumerator() { yield break; } // explicit interface member 'IEnumerable.GetEnumerator' IEnumerator IEnumerable.GetEnumerator() { yield break; } // explicit interface

I'm trying to log the contents of the HttpServletRequest attributes collection. I need to do this when the servlet first starts, and again right before the servlet is finished. I'm doing this in an attempt to understand a crufty and ill-maintained servlet. Because I need to have as little impact as possible, servlet filters are not an option. So here's the problem. When the servlet starts, I'll iterate through the enumeration returned by HttpServletRequest.getAttributeNames(). However, when I want to iterate through it again, getAttributeNames().hasMoreElements() returns "false"! I can't find

I've got two long streams of numbers coming from two different sources (binary data) in Ruby (1.9.2). The two sources are encapsulated in the form of two Enumerators . I want to check that the two streams are exactly equal. I've come with a couple solutions, but both seem quite inelegant. The first one simply transforms both into an array: def equal_streams?(s1, s2) s1.to_a == s2.to_a end This works, but it is not very performant, memory-wise, specially if the streams have lots of information. The other option is... ugh. def equal_streams?(s1, s2) s1.each do |e1| begin e2 = s2.next return

I'm basicly trying to make my class able to iterate using foreach . I read this tutorial. MSDN . It seems very straight forward. However, I have a problem when I want to iterate second time. I debugged it; and it turned out that it doesn't call the Reset() function. Class A class A : IEnumerable, IEnumerator { int[] data = { 0, 1, 2, 3, 4 }; int position = -1; public object Current { get { return data[position]; } } public bool MoveNext() { position++; return (position < data.Length); } public void Reset() { position = -1; } public IEnumerator GetEnumerator() { return (IEnumerator)this; } }

As per Ruby's documentation, the Enumerator object uses the each method (to enumerate) if no target method is provided to the to_enum or enum_for methods. Now, let's take the following monkey patch and its enumerator, as an example o = Object.new def o.each yield 1 yield 2 yield 3 end e = o.to_enum loop do puts e.next end Given that the Enumerator object uses the each method to answer when next is called, how do calls to the each method look like, every time next is called? Does the Enumeartor class pre-load all the contents of o.each and creates a local copy for enumeration? Or is there some

I have multithreads application and i get this error ************** Exception Text ************** System.InvalidOperationException: Collection was modified; enumeration operation may not execute. at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource) at System.Collections.Generic.List`1.Enumerator.MoveNextRare() at System.Collections.Generic.List`1.Enumerator.MoveNext() ... I probably have problem with my collection, because on one thread i read my collection and on another thread i modify collection. public readonly ObservableCollectionThreadSafe<GMapMarker> Markers