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  • Android: How to detect end of scroll

    - by Mix
    Hi! I need to implement HorizontalScrollView which is scrolled to predefined positions (similar to Home behaviour). It works with slow gestures, but does not work with flings. I hooked to View.onScrollChanged() and it is called when scrolling happened, but I can't determine when scrolling ends. In theory there should be a way to say that fling is over. Is there such API?

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  • domain specific languages and compilers

    - by hyperboreean
    I was looking over Martin Fowler's recent book contents - Domain Specific Languages and I noticed some ANTLR example - that got me thinking that writing compilers will become more and more popular since people needs in this matter will increase. So, will the compiler theory still be as arid (being subjective here) as it was until now or are there any chances that we'll get more applied, programmer oriented materials ?

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  • How can you animate a sprite in SFML (C++)

    - by Apoc
    Lets say I have 4 images and I want to use these 4 images to animate a character. The 4 images represent the character walking. I want the animation to repeat itself as long as I press the key to move but to stop right when I unpress it. It doesn't need to be SFML specific if you don't know it, just basic theory would really help me. Thank you.

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  • Odd ActiveRecord model dynamic initialization bug in production

    - by qfinder
    I've got an ActiveRecord (2.3.5) model that occasionally exhibits incorrect behavior that appears to be related to a problem in its dynamic initialization. Here's the code: class Widget < ActiveRecord::Base extend ActiveSupport::Memoizable serialize :settings VALID_SETTINGS = %w(show_on_sale show_upcoming show_current show_past) VALID_SETTINGS.each do |setting| class_eval %{ def #{setting}=(val); self.settings[:#{setting}] = (val == "1"); end def #{setting}; self.settings[:#{setting}]; end } end def initialize_settings self.settings ||= { :show_on_sale => true, :show_upcoming => true } end after_initialize :initialize_settings # All the other stuff the model does end The idea was to use a single record field (settings) to persist a bunch of configuration data for this object, but allow all the settings to seamlessly work with form helpers and the like. (Why this approach makes sense here is a little out of scope, but let's assume that it does.) Net-net, Widget should end up with instance methods (eg #show_on_sale= #show_on_sale) for all the entires in the VALID_SETTINGS array. Any default values should be specified in initialize_settings. And indeed this works, mostly. In dev and staging, no problems at all. But in production, the app sometimes ends up in a state where a) any writes to the dynamically generated setters fail and b) none of the default values appear to be set - although my leading theory is that the dynamically generated reader methods are just broken. The code, db, and environment is otherwise identical between the three. A typical error message / backtrace on the fail looks like: IndexError: index 141145 out of string (eval):2:in []=' (eval):2:inshow_on_sale=' [GEM_ROOT]/gems/activerecord-2.3.5/lib/active_record/base.rb:2746:in send' [GEM_ROOT]/gems/activerecord-2.3.5/lib/active_record/base.rb:2746:inattributes=' [GEM_ROOT]/gems/activerecord-2.3.5/lib/active_record/base.rb:2742:in each' [GEM_ROOT]/gems/activerecord-2.3.5/lib/active_record/base.rb:2742:inattributes=' [GEM_ROOT]/gems/activerecord-2.3.5/lib/active_record/base.rb:2634:in `update_attributes!' ...(then controller and all the way down) Ideas or theories as to what might be going on? My leading theory is that something is going wrong in instance initialization wherein the class instance variable settings is ending up as a string rather than a hash. This explains both the above setter failure (:show_on_sale is being used to index into the string) and the fact that getters don't work (an out of bounds [] call on a string just returns nil). But then how and why might settings occasionally end up as a string rather than hash?

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  • Good introductory statistics book?

    - by lmsasu
    Hello, what is a good introductory statistics book you can recommend? if there is a whole sequence of books that should be read, please do not hesitate to mention it. Books with applications are also welcome. I am aware that a single search on Amazon (or any other book seller) will provide me tons of titles, but some of them are avoidable... About my background/knowledge: good knowledge of mathematics and probability theory, but almost null on statistics.

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  • shortest directed odd cycle

    - by gleb-pendler
    6.1.4 Describe an algorithm based on breadth-first search for finding a shortest odd cycle in a graph. 6.3.5 Describe an algorithm based on directed breadth-first search for finding a shortest directed odd cycle in a digraph. what is most importent is that it must be a directed graph not necessary bfs but must be the shortest directed odd cycle!!! Question was taken from "Graph Theory" by J.A. Bondy and U.S.R. Murty thanks in advance!!!

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  • Best Planar graph program

    - by brian
    In graph theory, a planar graph is a graph that can be embedded in the plane, i.e., it can be drawn on the plane in such a way that its edges intersect only at their endpoints. What is the best open source program for drawing the planar graph with support of input nodes size and fixed drawing boundary region

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  • How would you handle making an array or list that would have more entries than the standard implemen

    - by faceless1_14
    I am trying to create an array or list that could handle in theory, given adequate hardware and such, as many as 100^100 BigInteger entries. The problem with using an array or standard list is that they can only hold Integer.MAX_VALUE number of entries. How would you work around this limitations? A whole new class/interface? A wrapper for list? another data type entirely?

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  • how good is java's UUID.randomUUID?

    - by Alvin
    I know randomized UUID have very very very low probability for collision in theory, but I am wondering, in practice, how good is java 5's randonUUID in terms of not having collision? Does anybody have any experience to share?

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  • Combined states, FSM

    - by bobobobo
    Not sure this is the right place to ask, but is it "correct" to combine states of an FSM? Say you have an object with enum State { State1 = 1 << 0, State2 = 1 << 1, State3 = 1 << 2 } ; It just so happens that it makes sense to combine states, as in State myState = State1 | State2 ; however in FSM theory is this illegal?

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  • Scala giving me "illegal start of definition"

    - by Malvolio
    I'm trying to get started with Scala and cannot get out of the starting gate. A file consisting of the line package x gives me error: illegal start of definition Regardless of what x is and regardless of where I put the file (I had a theory that I had to place the file in a directory hierarchy to match the package definition, but no). I get the same error with the example code from the web site and with the REPL.

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  • Parse tree and grammars information

    - by fuzzylogikk
    Do anyone know where to find good online resources with examples how to make grammars and parsetrees? Preferebly introductary materials. Info that is n00b friendly, haven't found anything good with google myself. edit: I'm thinking about theory, not a specific parser software.

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  • What situations does a Monostate pattern model?

    - by devoured elysium
    I know what both a Singleton or a Monostate are and how to implement them. Although I can see many uses for a Singleton, I can't imagine a situation where I would want to let the user create as many instances of my class although in reality only one really exists behind the scenes. Can anybody help me here? I know that for several reasons one should stay away from both patterns, but in theory, what kind of problems does the Monostate model? Thanks

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  • Lazy Loading wpf Combobox items

    - by Chris McGrath
    I have an IEnumerable< which lazy loads it's data. I want to just set a Combobox's ItemsSource to the IEnumerable, but when I do it goes and loads all the data anyway (which removes the point of lazy loading). I've tried it with Linq-To-Sql as well since it seems to be a similar theory and it also loads all the data. Is there an easy way to do this?

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  • Choosing colour schemes

    - by DanDan
    How do you choose your colour schemes for your applications and/or web designs? Is it a gut instinct thing or can logic be applied here too? I have looked at some colour theory but my combinations seemed wrong. I am looking at a monochrome webpage. Rather than pluck colours out of the air as usual I would like to see if there is a science behind this. Links and opinions welcome.

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  • SQL join: where clause vs. on clause

    - by BCS
    After reading it, this is not a duplicate of Explicit vs Implicit SQL Joins. The answer may be related (or even the same) but the question is different. What is the difference and what should go in each? If I understand the theory correctly, the query optimizer should be able to use both interchangeably.

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  • Enum type constraints in C#

    - by Taylor L
    What is the reason behind C# not allowing type constraints on Enum's? I'm sure there is a method behind the madness, but I'd like to understand why it's not possible. Below is what I would like to be able to do (in theory). public static T GetEnum<T>(this string description) where T : Enum { ... }

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  • Understanding colors

    - by Ankur Gupta
    Hello everyone, Kindly point towards theory/material to read for understanding colors and what makes a good color combinations. Mind it that I am not interested in say "Color combinations for web application" etc. More of the lines of say "Colors and humans". Material free to read is what i am looking for. Thanks

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  • lexers vs parsers

    - by Naveen
    Are lexers and parsers really that different in theory ? It seems fashionable to hate regular expressions: coding horror, another blog post. However, popular lexing based tools: pygments, geshi, or prettify, all use regular expressions. They seem to lex anything... When is lexing enough, when do you need EBNF ? Has anyone used the tokens produced by these lexers with bison or antlr parser generators?

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  • Cocoa for the non-techinical

    - by annoyed
    How would you describe and explain Cocoa in non-technical terms, with lots of analogies to common, everyday things. For example, imagine you are describing it to a 5-year-old who keeps asking why? at the end if each explanation. This would invariable delve into the theory of OO so it could get lengthy, but the concept is important to the 'why' of Cocoa.

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  • technologies beside scaling web applications in a distributed nature

    - by wik
    Hello, I am interested in theory to scale web applications in a distributed nature, i.e. when there is some platform/stack can be extended by others applications running on different servers, etc. I am researching this field and feels the lack of the right keywords :) Interesting concepts found so far: opensocial through API, like shopify does (shopify it's a hosted ecommerce solution) semantic web not quite sure about this one Am I on the right way or am I lost anything? :) Thanks.

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