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  Functional Programming For Object Oriented Programmers

After recently remarking about how I finally "got" functional programming I was asked by one of my millions of twitter followers... ¬_¬ to write up an explanation of a small F# program spoken in terms that fellow O-O programmers would understand. Before I become too entrenched into the functional programming way of thinking, that is, and can't explain it anymore. As a former tutor this is one of the major problems with being able to teach something once you understand it. You've ...

   Functional programming,OOP,F#,Pattern     2011-11-25 13:49:16

  How to read Haskell like Python

Have you ever been in the situation where you need to quickly understand what a piece of code in some unfamiliar language does? If the language looks a lot like what you’re comfortable with, you can usually guess what large amounts of the code does; even if you may not be completely familiar how all the language features work.For Haskell, this is a little more difficult, since Haskell syntax looks very different from traditional languages. But there's no really deep difference here; you j...

   Haskell,Python,Format,Like,Similarity     2011-11-15 08:45:39

  Rediscovering the RSync Algorithm

A:Ok, you’re synchronizing this over the web; and what do you use for the synchronization? B: Oh, we implemented the rsync algorithm. A: uhu. And what do you do with really big files? B: The same. A: And you also synchronise folders? B: Yes. A: And how do you do that? B: we iterate over the folder, using the algorithm on every file, recursing over subfolders. A: Can you try 2 things for me? First, a very large file; and second, a large codebase, and see if it holds. Introduction First ...

   ReSync algorithm,Discovery     2012-02-14 10:47:24

  True Scala complexity

Update 2: Sorry for the downtime. Leave it to the distributed systems guy to make his blog unavailable. Nginx saves the day.It’s always frustrating reading rants about Scala because they never articulate the actual complexities in the core language.Understandable—this post is intended fill that gap, and it wasn’t exactly easy to put together. But there’s been so much resistance to the very thought that the complexity exists at all, even from on up high, that I thou...

   Scala,Complexity     2012-01-10 07:17:07

  Optimization Tricks used by the Lockless Memory Allocator

With the releasing of the Lockless Memory Allocator under the GPL version 3.0 license, we can now discuss more of the optimization tricks used inside it. Many of these are things you wouldn't want to use in normal code. However, when speed is the ultimate goal, sometimes we need to break a few rules and use code that is a little sneaky.The SlabA slab is a well-known technique for allocating fixed size objects. For a given object size, a chunk of memory is divided up into smaller regions of that ...

   Optimization,Memory allocation     2011-11-16 08:02:16

  The trap of the performance sweet spot

This post is about JavaScript performance but I would like to start it by telling a story that might seem unrelated to JS. Please bear with me if you don’t like C.A story of a C programmer writing JavaScriptMr. C. is a C programmer as you can probably guess from his name. Today he was asked by his boss to write a very simple function: given an array of numbered 2d points calculate vector sum of all even numbered points... He opens his favorite text editor and quickly types somet...

   C,JavaScript,Sweet spot,Memory,Low level,Trap     2011-11-06 14:45:01

  Decision Trees in C#

Decision trees are simple predictive models which map input attributes to a target value using simple conditional rules. Trees are commonly used in problems whose solutions must be readily understandable or explainable by humans, such as in computer-aided diagnostics and credit analysis. Download source code Download sample applications Download the full Accord.NET Framework Introduction Decision Trees give a direct and intuitive way for obtaining the classification of a new instance f...

   C#,Decision tree     2012-03-23 10:00:56

  A re-introduction to JavaScript

Introduction Why a re-introduction? Because JavaScript has a reasonable claim to being the world's most misunderstood programming language. While often derided as a toy, beneath its deceptive simplicity lie some powerful language features. 2005 saw the launch of a number of high-profile JavaScript applications, showing that deeper knowledge of this technology is an important skill for any web developer. It's useful to start with an idea of the language's history. JavaScript was created in 1...

   JavaScript,Types,Array,Re-introduction,OOP     2012-02-09 05:38:08

  Why (offset, limit) is slow in database select?

Starting from a problem Five years ago when I was working at Tencent, I found that MySQL request speed was very slow in the pagination scenario. With only 100,000 data, a select query on a single machine took about 2-3 seconds. I asked my mentor why, and he asked in return, "In an indexing scenario, what is the time complexity to get the nth largest number in MySQL?" The pursuit of the answer Confirming the scenario Assuming there is an index on the "status" column, a query like "select * from t...

   SLOW,LIMIT,OFFSET,MYSQL     2023-03-12 05:21:02

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