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  Translating math into code with examples in Java, Racket, Haskell and Python

Discrete mathematical structures form the foundation of computer science.These structures are so universal that most research papers in the theory of computation, programming languages and formal methods present concepts in terms of discrete mathematics rather than code.The underlying assumption is that the reader will know how to translate these structures into a faithful implementation as a working program.A lack of material explaining this translation frustrates outsiders.What deepens that fr...

   Math,Algorithms,Formula,Program,Python     2011-11-14 08:43:15

  Additional steps need to implement to setup shadow-boxV2 OPTEE on Raspberry PI

We followed the Shadow-box v2 project from the https://github.com/kkamagui/shadow-box-for-arm to set up the trustZone on Raspberry PI modeB to protect the Linux Kernel. But got a problem when doing the step: [3.6.5. Activate Shadow-Box for ARM and Start Secure Pi!] to create the hash for the memory area. The result is not shown. If you met the same problem, this is what I did to fix the problem on my PI: 1.1  When we do the step [3.5.1. Copy OP-TEE OS with Shadow-Box for ARM and N...

   HARDWARE,RASPBERRY PI     2019-05-20 08:52:55

  One thought about JavaScript exception handle

Due to network, browser and cache issues, the JS executed in production may produce different results from the testing environments. Sometimes they may produce exceptions. Front-end developers may encounter this kind of exceptions frequently. But how to log and use them is seldomly considered by them. Actually, exception handling includes two steps : log and use. 1. Log Regarding to log error, this is relatively convenient, since in each browser, there is one interface called window.onerror. win...

   JaavScript,Log,Exception,Email     2013-03-18 12:50:21

  JSON in JavaScript

When sending an AJAX request to the server, the response can have two formats : XMLHttpRequest.responseXML to access data with XML format and XMLHttpRequest.responseText to access data with string format. XML is the standard data transfer format, but one weakness is it's troublesome to parse and retrieve the data. JSON(JavaScript Object Notation) is a light weight data interchange format, we call it the JavaScript object representation. The advantage of using JSON as the data format is itself is...

   JSON,JavaScript     2013-05-04 23:25:57

  How To Optimize Your Site With HTTP Caching

I’ve been on a web tweaking kick lately: how to speed up your javascript, gzip files with your server, and now how to set up caching. But the reason is simple: site performance is a feature. For web sites, speed may be feature #1. Users hate waiting, we get frustrated by buffering videos and pages that pop together as images slowly load. It’s a jarring (aka bad) user experience. Time invested in site optimization is well worth it, so let’s dive in. What is Caching? ...

   Website performance,Speed,HTTP Cache,Hash code     2011-12-10 06:11:33

  <=> operator in MySQL

Have you ever seen "<=>" in a SQL query while using MySQL? Does it mean less and equals to and greater than? Actually if you consider it as the union of <= and =>, great, you are close to it. This is one form of equal operator in MySQL, it has the similar meaning to the = operator with some subtle difference. According to MySQL documentation, <=> is NULL-safe equal. This operator performs an equality comparison like the = operator, but returns 1 rather than NULL if both operand...

   MySQL,NULL safe,<=>     2014-03-24 06:23:22

  Bash Shell Scripting - 10 Seconds Guide

This Bash shell scripting guide is not a detailed study but a quick reference to the BASH syntax. So lets begin... Common environment variables PATH - Sets the search path for any executable command. Similar to the PATH variable in MSDOS. HOME - Home directory of the user. MAIL - Contains the path to the location where mail addressed to the user is stored. IFS - Contains a string of characters which are used as word seperators in the command line. The string normally consists of the spac...

   Bash,Shell,Linux,Tutorial,10 seconds,Shortcut key     2012-02-28 08:05:41

  In-memory key-value store in C, Go and Python

Subtitle: Wow Go’s net library is fast On paternity leave for my second child, I found myself writing an in-memory hashmap (a poor-man’s memcached), in Go, Python and C. I was wondering how hard it would be to replace memcached, if we wanted to do something unusual with our key-value store. I also wanted to compare the languages, and, well, I get bored easily! The code is on github as Key-Value-Polyglot. Each version implements enough of the get and set commands from the mem...

   key-value,Memory,C,Python,Go     2012-03-21 09:21:51

  How does MySQL handle DROP TABLE

A few days ago, when executing DROP TABLE in MySQL, all processes including DDL and DML were hung until DROP TABLE was completed. I am confused about this phenomenon. I have reviewed the source codes of MySQL to check how MySQL internally handle DROP TABLE. When user trigger DROP TABLE command: ########################MySQL SERVER drop table######################## /* Sql_table.cc  delete (drop) tables. */bool mysql_rm_table( )   /*   Execute the drop of a normal or temporary...

   MySQL,DROP TABLE     2012-09-24 11:34:05

  What's Wrong with the For Loop

Closures in Java are a hot topic of late. A few really smart people are drafting a proposal to add closures to a future version of the language. However, the proposed syntax and the linguistic addition are getting a lot of push back from many Java programmers. Today, Elliotte Rusty Harold posted his doubts about the merits of closures in Java. Specifically, he asks "Why Hate the for Loop?": I don’t know what it is some people have against for loops that they’re so eager to...

   For loop,Basic,Problem,Efficiency,Java     2012-02-24 05:06:15

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