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In this post we’ll cover the second of the “basic four” methods of proof: the contrapositive implication. We will build off our material from last time and start by defining functions on sets. Functions as Sets So far we have become comfortable with the definition of a set, but the most common way to use sets is to construct functions between them. As programmers we readily understand the nature of a function, but how can we define one math..
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In this post we’ll cover the second of the “basic four” methods of proof: the contrapositive implication. We will build off our material from last time and start by defining functions on sets. Functions as Sets So far we have become comfortable with the definition of a set, but the most common way to use sets is to construct functions between them. As programmers we readily understand the nature of a function, but how can we define one math..
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In this post we’ll cover the second of the “basic four” methods of proof: the contrapositive implication. We will build off our material from last time and start by defining functions on sets. Functions as Sets So far we have become comfortable with the definition of a set, but the most common way to use sets is to construct functions between them. As programmers we readily understand the nature of a function, but how can we define one math..
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Thank you for attending the Exadata Snapper (ExaSnapper) hacking session! I have split the recording of this session into 3 pieces and uploaded to enkitec.tv . The ExaSnapper beta that I demoed is also available now in my blog. See the links below. For quick reference, here’s the syntax of running ExaSnapper – there are two modes, one is the before/after capture (think Tom Kyte’s runstats, but for exadata metrics) and the other is mo....
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Thank you for attending the Exadata Snapper (ExaSnapper) hacking session! I have split the recording of this session into 3 pieces and uploaded to enkitec.tv . The ExaSnapper beta that I demoed is also available now in my blog. See the links below. For quick reference, here’s the syntax of running ExaSnapper – there are two modes, one is the before/after capture (think Tom Kyte’s runstats, but for exadata metrics) and the other is mo....
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Speaking of Marco Arment , yesterday he posted an article called The first “Read Later” service in which he discussed the origins of Instapaper and the service that was eventually rebranded as Pocket: “Months after Instapaper launched all of these features and was being very well-received in the tech press, in October 2008, Read It Later added a web service for sync, other-browser bookmarklets, and offline saving. Then an iPhone app....
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Marco Arment gave Jacob Goldstein of NPR some concrete numbers for the Magazine, showing just how great an idea launching this publication was, the importance of a consistent publication schedule, and the rewards of such an excellent implementation. “Last fall, Marco Arment launched a general interest magazine. It’s called, aptly enough, The Magazine. Writers are paid $800 per article. There are no ads. Until recently, it was available ..
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With years of programming under my belt and currently taking a philosophy course, I found the parallels a blogger writing under the moniker “panefsky” drew between programming, philosophy, and specific philosophers interesting. “It is perfectly reasonable to consider the programming languages as the different philosophies of a virtual world, in which entities do exist and interact with each other. To this respect, even the fundamental p..
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We are at the very beginning of the build process,’ Dave Bedwood, creative partner at Lean Mean Fighting Machine, said in an email. ‘This site is very much for people to sign up now, get a second twitter account, private to them, and just watch it learn and grow. As A.I advances, then maybe we will then get into it being able to copy syntax. When you die, if you’ve had this account for a long time, it may be able to keep tweeting as you.’” ..
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Two of my favorite libraries in C#: FluentAssertions and NUnit (of course). NUnit has a “hidden” gem (that is, it’s well documented, yet few developers use it): [TestCase]. Look at this: using FluentAssertions; using NUnit.Framework; public class RomanNumeralsTest { [TestCase(3333, "MMMCCCXXXIII")] [TestCase(555, "DLV")] [TestCase(999, "CMXCIX")] [TestCase(444, "CDXLIV")] public void ItConvertsNumbersToRomanNumerals(int number, string roman..
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When I scrolled past this article on Hacker News late last night, I wasn’t quite sure what to expect. I certainly wasn’t expecting to see remote control quadracopters (flying vehicles with four rotors instead of one as in a helicopter) balancing, throwing, and catching a large pendulum with practiced precision. To my amazement though, that’s exactly what I found, along with another video showing two similar quadracopters juggling a ball ba..
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Kenneth Erikson tells his amazing life story in an article titled I’m a shut-in. This is my story . No matter what I try I can’t quite capture the essence of this intensely personal piece, so I will leave you with this excerpt and the strongest urging possible to set aside a good hour to read K-2052’s amazing story from beginning to end. “If you’re fake for long enough you’ll eventually start to fake yourself. The same tricks you pull ..
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'Futures' are a great addition to the software developer's toolkit
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www.databasesandlife.com
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13 years ago
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eng
I like things happening in parallel but which don't require mental effort thinking about synchronization and race conditions etc; i.e. where one can write code that basically looks like sequential code but is actually parallel. Futures, backed by threads, which are trivial to implement in Java, are great at this. My employee Martin’s written some code to fetch data (friends) from various connected accounts, which currently can include: ..
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After my last post I had a variety of readers reach out about many different tweaks they’d made to their workflows using with psql. One people Grégoire Hubert had a wondeful extensive list of items. Grégoire has been a freelance in web development and he has worked with Postgresql for some time now in addition to being the author of Pomm. Without further ado heres what he has to say on how he uses psql: Get the most of psql Psql,....
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After my last post I had a variety of readers reach out about many different tweaks they’d made to their workflows using with psql. One people Grégoire Hubert had a wondeful extensive list of items. Grégoire has been a freelance in web development and he has worked with Postgresql for some time now in addition to being the author of Pomm. Without further ado heres what he has to say on how he uses psql: Get the most of psql Psql,....
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Quite some time ago I came across Jeffrey Way’s article Publishers: Don’t Restrict Writers and added it to my Instapaper queue more out of curiosity at an article posted on Nettuts+ not about programming than anything else. Nearly a month prior, I had read an article on Ben Brooks’ website called Self-Publishing in which he said something I found very interesting: Permalink.
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Yesterday marks the tenth day since I last made a post to this site, the tenth day spent doing other things besides reading and writing in every free moment of my day; today marks the eleventh day since that last post went live, and the day I have decided to return to that lifestyle. Permalink.
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Peeking into Linux kernel-land using /proc filesystem for quick’n’dirty troubleshooting
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tanelpoder.com
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13 years ago
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eng
This blog entry is about modern Linuxes. In other words RHEL6 equivalents with 2.6.3x kernels and not the ancient RHEL5 with 2.6.18 kernel (wtf?!), which is the most common in enterprises unfortunately. And no, I’m not going to use kernel debuggers or SystemTap scripts here, just plain old “cat /proc/PID/xyz” commands against some useful /proc filesystem entries. Troubleshooting a “slow” process Here’s one systematic troubleshooting examp....
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Peeking into Linux kernel-land using /proc filesystem for quick’n’dirty troubleshooting
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tanelpoder.com
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13 years ago
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eng
This blog entry is about modern Linuxes. In other words RHEL6 equivalents with 2.6.3x kernels and not the ancient RHEL5 with 2.6.18 kernel (wtf?!), which is the most common in enterprises unfortunately. And no, I’m not going to use kernel debuggers or SystemTap scripts here, just plain old “cat /proc/PID/xyz” commands against some useful /proc filesystem entries. Troubleshooting a “slow” process Here’s one systematic troubleshooting examp....
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Learn the best approach to center content in UIScrollView using contentInset instead of layoutSubviews or setContentOffset for better zooming behavior.
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Hi All, This is a bit of an odd one but today I got one of the most abusive support requests I’ve ever received and realised I’ve never really talked about these. To clarify I’m all up for criticism of the app and suggestions on improvements, here I’m referring to out right abuse with terrible language and personal insults. While they’re actually quite rare you’d be impressed that they do come through and they aren’t pretty.
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Dear readers, I’ve started the slow migration of code from puppet 2.6 all the way to 3.x+. There were a few things I wasn’t clear on, so hopefully this will help to discuss these and make your migration easier! I used hiera in 2.6, and I actually like it a lot so far. I was concerned that automatic lookups would pull in values that I wasn’t expecting. This is not the case or a worry. Let’s dive in and let the code speak:
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Dear readers, I’ve started the slow migration of code from puppet 2.6 all the way to 3.x+. There were a few things I wasn’t clear on, so hopefully this will help to discuss these and make your migration easier! I used hiera in 2.6, and I actually like it a lot so far. I was concerned that automatic lookups would pull in values that I wasn’t expecting. This is not the case or a worry. Let’s dive in and let the code speak:
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There are many short methods in the Apache Commons libraries that seem like overkill at first glance, however, their purpose becomes more apparent when you examine the effect that these methods have on the readability of the caller. I see a lot of code that does stuff like this: if( s == null || "".equals(s.trim())) { // Do something } which could be re-written as if( StringUtils.isBlank(s)) { // Do something } Personally, I..
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I often have this need to remove some keys from a list of dict, like cleaning it before passing it. Comment on Gist
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Always Use a "default" Clause in a "switch" Statement
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www.databasesandlife.com
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13 years ago
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eng
The following [question]( http://stackoverflow.com/questions/4649423/should-switch-statements-always-contain-a-default-clause/4649518#4649518" target="_blank">http://stackoverflow.com/questions/4649423/should-switch-statements-always-contain-a-default-clause/4649518) was asked on Stack Overflow: I was told that it’s good practice to include a default clause in all switch statements. I recently remembered this advice but can’t remember ..
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If you already downloaded snapper v4, then better re-download it again as the v4.03 also runs in SQL Developer! You might also want to check how to enable the DBMS_OUTPUT display in SQL Developer post by “That” Jeff Smith :-) Update: Niall Litchfield pointed out that the “set serverout on” command was ignored on SQL Developer because I was using the short syntax (server out instead of server output ). Once I changed this,..
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If you already downloaded snapper v4, then better re-download it again as the v4.03 also runs in SQL Developer! You might also want to check how to enable the DBMS_OUTPUT display in SQL Developer post by “That” Jeff Smith :-) Update: Niall Litchfield pointed out that the “set serverout on” command was ignored on SQL Developer because I was using the short syntax (server out instead of server output ). Once I changed this,..
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Snapper used to require access to DBMS_LOCK, so it could sleep for X seconds between the “before” and “after” performance data snapshots. Now it is possible to get away without using DBMS_LOCK. Instead you will run Snapper twice, once for taking the “before” snapshot, then run your workload and then run Snapper again for taking the “after” snapshot and print the output. So, the usual way of running snapper is this:
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Snapper used to require access to DBMS_LOCK, so it could sleep for X seconds between the “before” and “after” performance data snapshots. Now it is possible to get away without using DBMS_LOCK. Instead you will run Snapper twice, once for taking the “before” snapshot, then run your workload and then run Snapper again for taking the “after” snapshot and print the output. So, the usual way of running snapper is this:
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I have fixed most of the bugs that showed up during the Snapper launch party session and uploaded the new version (v4) of Snapper here: https://github.com/tanelpoder/tpt-oracle/blob/master/snapper.sql I have uploaded some of my videos to https://www.youtube.com/tanelpoder : Snapper & Ashtop Overview Snapper v4 Launch Party video (old) I have not updated the snapper documentation yet, but here are the main improvemen..
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I have fixed most of the bugs that showed up during the Snapper launch party session and uploaded the new version (v4) of Snapper here: https://github.com/tanelpoder/tpt-oracle/blob/master/snapper.sql I have uploaded some of my videos to https://www.youtube.com/tanelpoder : Snapper & Ashtop Overview Snapper v4 Launch Party video (old) I have not updated the snapper documentation yet, but here are the main improvemen..
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You can find the code here on github and the package here on PyPi I have written and continue to maintain a reporting system for a group of pentesters. During/after the tests the results and details are inputted into a web application using a WYSIWYG editor called Redactor (which is pretty awesome!)...
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You can find the code here on github and the package here on PyPi I have written and continue to maintain a reporting system for a group of pentesters. During/after the tests the results and details are inputted into a web application using a WYSIWYG editor called Redactor (which is pretty awesome!)...
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Back in December of 2004 I started a new life from zero. I was 22 years old without any money, education or connections. I borrowed my mothers computer and started to learn HTML and internet marketing. That is now 8 years ago and each year I publish an annual report. Earlier reports are linked from [...]
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Back in December of 2004 I started a new life from zero. I was 22 years old without any money, education or connections. I borrowed my mothers computer and started to learn HTML and internet marketing. That is now 8 years ago and each year I publish an annual report. Earlier reports are linked from [...]
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I recently posted an exploratory piece on why programmers who are genuinely interested in improving their mathematical skills can quickly lose stamina or be deterred. My argument was essentially that they don’t focus enough on mastering the basic methods of proof before attempting to read research papers that assume such knowledge. Also, there are a number of confusing (but in the end helpful) idiosyncrasies in mathematical culture that are..
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