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  • Function from other module not detecting

    - by Lethi
    I two modules in same src folder. mod1 declares function I wish to use in module mod2: -module(mod1). -export([myfunc/1]). myfunc(A) -> {ok}. In other module I not import mod1: -module(mod2). If I do "mod1:" in mod2 it recognizes "myfunc", problem is at run-time when I call mod1:myfunc(A) I get "undefined function mod1:myfunc/1" I not understand why I get error if intellisense detect my mod1 function in mod2?

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  • Is CDS a valid analogy for pointers? [closed]

    - by Flinkman
    So.. bear with me. I just found an analogy to c++ pointers and CDS. This clip describes CDS(Credit Default Swaps). http://www.youtube.com/watch?v=KPNdYtrlgaU#t=120s "Here we know we have an instrument of a particular financial instrument that is demonstrably dangerous, it creates long chains of risk which are vulnerable to the failure of individual trader or market partipants, in that chain and these instruments in an affect permit the creation of vicious spirals. In which the CDS price interact with the bound price, the market price and you can have a downward spiral." What my ears are telling me: "Don't create dependences that will create long chains of crashing systems." Update: Trying to clarify with something that is closer to the readers. If I change the words: instrument = construct financial = language trader = object market partipants = c structs CDS price = uptime bound price = outcome market price = ROI(return on incestment) The quote become more understandable. Look: "Here we know we have construct of a particular language construct that is demonstrably dangerous, it creates long chains of risk which are vulnerable to the failure of individual object or structs in that chain and these system in an affect permit the creation of vicious spirals. In which the uptime interact with the outcome, the ROI and you can have a downward spiral."

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  • What is the rationale behind snazzy Window Managers/Composers?

    - by Emanuele
    This is more of a generic question, based on trying out Window Managers like Awesome, Mate and others. To me looks like that other Window Managers like Gnome3 and/or Unity are heavy and pointless. I do understand that having all the composed UIs is more pleasant for the eye, but apart that, what are the other major benefits? To make an example, when I run the game Heroes of Newerth (using nVidia drivers) under: Unity : the FPS drops sharply Gnome3 : FPS is ok, but X and other processes use 15~20% of CPU and quite some additional memory Awesome : FPS is ok, and other processes use very little memory and CPU Below some numbers regarding what I'm saying (please note my system is 64 bit, AMD Phenom II X4, 8 GB RAM, nd nVidia 470 GTX, SSD disk). All data is sorted by mem usage (watch -d -n 10 "ps -e -o pcpu,pmem,pid,user,cmd --sort=-pmem | head -20"); again note that CPU time of ./hon-x86_64 might be different due to the fact I can't take the snapshot of the system during exactly same time. Awesome: %CPU %MEM PID USER CMD 91.8 21.6 3579 ema ./hon-x86_64 2.4 0.9 3223 root /usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch 1.6 0.4 2600 ema /usr/lib/erlang/erts-5.8.5/bin/beam.smp -Bd -K true -A 4 -- -root /usr/lib/erlang -progname erl -- -home /home/ema -- -noshell -noinp 0.3 0.2 3602 ema gnome-terminal 0.0 0.2 2698 ema /usr/bin/python /usr/lib/desktopcouch/desktopcouch-service Gnome3: %CPU %MEM PID USER CMD 82.7 21.0 5528 ema ./hon-x86_64 17.7 1.7 5315 ema /usr/bin/gnome-shell 5.8 1.2 5062 root /usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch 1.0 0.4 5657 ema /usr/bin/python /usr/lib/ubuntuone-client/ubuntuone-syncdaemon 0.7 0.3 5331 ema nautilus -n 1.6 0.3 2600 ema /usr/lib/erlang/erts-5.8.5/bin/beam.smp -Bd -K true -A 4 -- -root /usr/lib/erlang -progname erl -- -home /home/ema -- - 0.9 0.2 5451 ema gnome-terminal 0.1 0.2 5400 ema /usr/bin/python /usr/lib/desktopcouch/desktopcouch-service Unity 3D: %CPU %MEM PID USER CMD 87.2 21.1 6554 ema ./hon-x86_64 10.7 2.6 6105 ema compiz 17.8 1.1 5842 root /usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch 1.3 0.9 6672 root /usr/bin/python /usr/sbin/aptd 0.4 0.4 6606 ema /usr/bin/python /usr/lib/ubuntuone-client/ubuntuone-syncdaemon 0.5 0.3 6115 ema nautilus -n 1.5 0.3 2600 ema /usr/lib/erlang/erts-5.8.5/bin/beam.smp -Bd -K true -A 4 -- -root /usr/lib/erlang -progname erl -- -home /home/ema -- -noshell -noinput -sasl errl 0.3 0.2 6180 ema /usr/lib/unity/unity-panel-service So my point is, what's the rationale behind going towards such heavy WMs/Composers?

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  • What scalability problems have you solved using a NoSQL data store?

    - by knorv
    NoSQL refers to non-relational data stores that break with the history of relational databases and ACID guarantees. Popular open source NoSQL data stores include: Cassandra (tabular, written in Java, used by Facebook, Twitter, Digg, Rackspace, Mahalo and Reddit) CouchDB (document, written in Erlang, used by Engine Yard and BBC) Dynomite (key-value, written in C++, used by Powerset) HBase (key-value, written in Java, used by Bing) Hypertable (tabular, written in C++, used by Baidu) Kai (key-value, written in Erlang) MemcacheDB (key-value, written in C, used by Reddit) MongoDB (document, written in C++, used by Sourceforge, Github, Electronic Arts and NY Times) Neo4j (graph, written in Java, used by Swedish Universities) Project Voldemort (key-value, written in Java, used by LinkedIn) Redis (key-value, written in C, used by Engine Yard, Github and Craigslist) Riak (key-value, written in Erlang, used by Comcast and Mochi Media) Ringo (key-value, written in Erlang, used by Nokia) Scalaris (key-value, written in Erlang, used by OnScale) ThruDB (document, written in C++, used by JunkDepot.com) Tokyo Cabinet/Tokyo Tyrant (key-value, written in C, used by Mixi.jp (Japanese social networking site)) I'd like to know about specific problems you - the SO reader - have solved using data stores and what NoSQL data store you used. Questions: What scalability problems have you used NoSQL data stores to solve? What NoSQL data store did you use? What database did you use before switching to a NoSQL data store? I'm looking for first-hand experiences, so please do not answer unless you have that.

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  • PHP tag cloud ( and finding similar ones )

    - by mfolnovich
    Hello! I have articles on my site, and I would like to add tags which would describe each article, but I'm having problems with design mysql table for tags. I have two ideas: 1) each article would have field "tags", and tags would be in format: "tag1,tag2,tag3" 2) create other table called tags with fields: tag_name, article_id, so when I want tags for article with ID 1, I would run SELECT ... FROM tags WHERE news_id=1; But, I would also like to know 3 similar articles by comparing tags, so if I have article which has tags "php,mysql,erlang", and 5 articles with tags: "php,mysql", "erlang,ruby", "php erlang", "mysql,erlang,javascript", I would choose 1., 3. and 4., since those 3 have most same tags with main article. Thanks!

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  • Understanding mongod log entries

    - by Jo Erlang
    Can anyone explain the numbers in the % column, in this mongod log snippet ? It is building a new index but I'm not sure I understand why the numbers look like that Tue Nov 20 11:38:08 [initandlisten] connection accepted from 127.0.0.1:49299 #8 (2 connections now open) Tue Nov 20 11:38:08 [conn8] build index xx.yyyy { source: 1 } Tue Nov 20 11:38:19 [conn8] 2921300/243339 1200% Tue Nov 20 11:38:29 [conn8] 4109600/243339 1688% Tue Nov 20 11:38:39 [conn8] 4400100/243339 1808% Tue Nov 20 11:38:49 [conn8] 4676600/243339 1921% Tue Nov 20 11:38:59 [conn8] 4939700/243339 2029% Tue Nov 20 11:39:09 [conn8] 5217800/243339 2144% Tue Nov 20 11:39:19 [conn8] 5439300/243339 2235% Tue Nov 20 11:39:29 [conn8] 5659700/243339 2325% Thanks

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  • Unable to send mail to hotmail from rackspace cloud

    - by Jo Erlang
    I'm having issue sending mail from postfix on a rackspace cloud instance for my domain. Hotmail says "550 SC-001 (SNT0-MC4-F35) Unfortunately, messages from 198.101.x.x weren't sent. Please contact your Internet service provider since part of their network is on our block list. " Here is the mail log Sep 20 08:02:59 mydomain postfix/smtpd[1810]: disconnect from localhost[127.0.0.1] Sep 20 08:02:59 mydomain postfix/smtp[1814]: 59CFF4B191: to=<[email protected]>, relay=mx3.hotmail.com[65.55.92.184]:25, delay=0.19, delays=0.1/0.01/0.06/0.01, dsn=5.0.0, status=bounced (host mx3.hotmail.com[65.55.92.184] said: 550 SC-001 (SNT0-MC4-F35) Unfortunately, messages from 198.101.x.x weren't sent. Please contact your Internet service provider since part of their network is on our block list. You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. (in reply to MAIL FROM command)) Sep 20 08:02:59 mydomain postfix/smtp[1814]: 59CFF4B191: lost connection with mx3.hotmail.com[65.55.92.184] while sending RCPT TO I have implemented rDNS, SPF and DKIM they all are looking fine. I have checked my IP and domain, on most of the spam black lists and it is listed as ok on those, (not listed as spamming IP) What should I try next?

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  • Apache rewrite redirect to https and www

    - by Jo Erlang
    I need to get mod_rewrite to do the following http://abc.com -> https://www.abc.com https://abc.com/login -> https://www.abc.com/login http://www.abc.com?x=3 -> https://www.abc.com?x=3 https://abc.com/login?x=1 -> https://www.abc.com/login?x=1 http://www.abc.com/login?x=3 -> https://www.abc.com/login I have the following, in my abc.com.conf vhost file but its not work correctly <VirtualHost *:80> ServerName abc.com ServerAlias www.abc.com RewriteCond %{HTTP_HOST} ^abc\.com RewriteRule ^(.*)$ https://www.abc.com/$1 [R=permanent,L] RewriteCond %{HTTPS} off RewriteRule (.*) https://www.abc.com/%{REQUEST_URI} </VirtualHost> <VirtualHost *:443> ServerName abc.com ServerAlias www.abc.com RewriteCond %{HTTP_HOST} ^abc\.com RewriteRule ^(.*)$ https://www.abc.com/$1 [R=permanent,L] </VirtualHost> Can anyone help me out on the rest? [edited to clarify]

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  • Ejabberd clustering problem with amazon EC2 server

    - by user353362
    Hello Guys! I have been trying to install ejabberd server on Amazons EC2 instance. I am kinds a stuck at this step right now. I am following this guide: http://tdewolf.blogspot.com/2009/07/clustering-ejabberd-nodes-using-mnes... From the guide I have sucessfully completed the Set up First Node (on ejabberd1) part. But am stuck in part 4 of Set up Second Node (on ejabberd2) So all in all, I created the main node and am able to run the server on that node and access its admin console from then internet. In the second node I have installed ejabberd. But I am stuck at point 4 of setting up the node instruction presented in this blog (http://tdewolf.blogspot.com/2009/07/clustering-ejabberd-nodes-using-mnes...). I execute this command " erl -sname ejabberd@domU-12-31-39-0F-7D-14 -mnesia dir '"/var/lib/ejabberd/"' -mnesia extra_db_nodes "['ejabberd@domU-12-31-39-02-C8-36']" -s mnesia " on the second server and get a crashing error: root@domU-12-31-39-0F-7D-14:/var/lib/ejabberd# erl -sname ejabberd@domU-12-31-39-0F-7D-14 -mnesia dir '"/var/lib/ejabberd/"' -mnesia extra_db_nodes "['ejabberd@domU-12-31-39-02-C8-36']" -s mnesia {error_logger,{{2010,5,28},{23,52,25}},"Protocol: ~p: register error: ~p~n",["inet_tcp",{{badmatch,{error,duplicate_name}},[{inet_tcp_dist,listen,1},{net_kernel,start_protos,4},{net_kernel,start_protos,3},{net_kernel,init_node,2},{net_kernel,init,1},{gen_server,init_it,6},{proc_lib,init_p_do_apply,3}]}]} {error_logger,{{2010,5,28},{23,52,25}},crash_report,[[{pid,<0.21.0},{registered_name,net_kernel},{error_info,{exit,{error,badarg},[{gen_server,init_it,6},{proc_lib,init_p_do_apply,3}]}},{initial_call,{net_kernel,init,['Argument__1']}},{ancestors,[net_sup,kernel_sup,<0.8.0]},{messages,[]},{links,[#Port<0.52,<0.18.0]},{dictionary,[{longnames,false}]},{trap_exit,true},{status,running},{heap_size,610},{stack_size,23},{reductions,518}],[]]} {error_logger,{{2010,5,28},{23,52,25}},supervisor_report,[{supervisor,{local,net_sup}},{errorContext,start_error},{reason,{'EXIT',nodistribution}},{offender,[{pid,undefined},{name,net_kernel},{mfa,{net_kernel,start_link,[['ejabberd@domU-12-31-39-0F-7D-14',shortnames]]}},{restart_type,permanent},{shutdown,2000},{child_type,worker}]}]} {error_logger,{{2010,5,28},{23,52,25}},supervisor_report,[{supervisor,{local,kernel_sup}},{errorContext,start_error},{reason,shutdown},{offender,[{pid,undefined},{name,net_sup},{mfa,{erl_distribution,start_link,[]}},{restart_type,permanent},{shutdown,infinity},{child_type,supervisor}]}]} {error_logger,{{2010,5,28},{23,52,25}},crash_report,[[{pid,<0.7.0},{registered_name,[]},{error_info,{exit,{shutdown,{kernel,start,[normal,[]]}},[{application_master,init,4},{proc_lib,init_p_do_apply,3}]}},{initial_call,{application_master,init,['Argument_1','Argument_2','Argument_3','Argument_4']}},{ancestors,[<0.6.0]},{messages,[{'EXIT',<0.8.0,normal}]},{links,[<0.6.0,<0.5.0]},{dictionary,[]},{trap_exit,true},{status,running},{heap_size,233},{stack_size,23},{reductions,123}],[]]} {error_logger,{{2010,5,28},{23,52,25}},std_info,[{application,kernel},{exited,{shutdown,{kernel,start,[normal,[]]}}},{type,permanent}]} {"Kernel pid terminated",application_controller,"{application_start_failure,kernel,{shutdown,{kernel,start,[normal,[]]}}}"} Crash dump was written to: erl_crash.dump Kernel pid terminated (application_controller) ({application_start_failure,kernel,{shutdown,{kernel,start,[normal,[]]}}}) root@domU-12-31-39-0F-7D-14:/var/lib/ejabberd# any idea what going on? I am not really sure how to solve this problem :S how to let ejabberd only access register from one special server? › Is that the right way of copying .erlang.cookie file? Submitted by privateson on Sat, 2010-05-29 00:11. before this I was getting this error (see below), I solved it by running this command: chmod 400 .erlang.cookie Also to copy the cookie I simply created a file using vi on the second server and copied the secret code from server one to the second server. Is that the right way of copying .erlang.cookie file? ERROR ~~~~~~~~~~ root@domU-12-31-39-0F-7D-14:/etc/ejabberd# erl -sname ejabberd@domU-12-31-39-0F-7D-14 -mnesia dir '"/var/lib/ejabberd/"' -mnesia extra_db_nodes "['ejabberd@domU-12-31-39-02-C8-36']" -s mnesia {error_logger,{{2010,5,28},{23,28,56}},"Cookie file /root/.erlang.cookie must be accessible by owner only",[]} {error_logger,{{2010,5,28},{23,28,56}},crash_report,[[{pid,<0.20.0},{registered_name,auth},{error_info,{exit,{"Cookie file /root/.erlang.cookie must be accessible by owner only",[{auth,init_cookie,0},{auth,init,1},{gen_server,init_it,6},{proc_lib,init_p_do_apply,3}]},[{gen_server,init_it,6},{proc_lib,init_p_do_apply,3}]}},{initial_call,{auth,init,['Argument__1']}},{ancestors,[net_sup,kernel_sup,<0.8.0]},{messages,[]},{links,[<0.18.0]},{dictionary,[]},{trap_exit,true},{status,running},{heap_size,987},{stack_size,23},{reductions,439}],[]]} {error_logger,{{2010,5,28},{23,28,56}},supervisor_report,[{supervisor,{local,net_sup}},{errorContext,start_error},{reason,{"Cookie file /root/.erlang.cookie must be accessible by owner only",[{auth,init_cookie,0},{auth,init,1},{gen_server,init_it,6},{proc_lib,init_p_do_apply,3}]}},{offender,[{pid,undefined},{name,auth},{mfa,{auth,start_link,[]}},{restart_type,permanent},{shutdown,2000},{child_type,worker}]}]} {error_logger,{{2010,5,28},{23,28,56}},supervisor_report,[{supervisor,{local,kernel_sup}},{errorContext,start_error},{reason,shutdown},{offender,[{pid,undefined},{name,net_sup},{mfa,{erl_distribution,start_link,[]}},{restart_type,permanent},{shutdown,infinity},{child_type,supervisor}]}]} {error_logger,{{2010,5,28},{23,28,56}},crash_report,[[{pid,<0.7.0},{registered_name,[]},{error_info,{exit,{shutdown,{kernel,start,[normal,[]]}},[{application_master,init,4},{proc_lib,init_p_do_apply,3}]}},{initial_call,{application_master,init,['Argument_1','Argument_2','Argument_3','Argument_4']}},{ancestors,[<0.6.0]},{messages,[{'EXIT',<0.8.0,normal}]},{links,[<0.6.0,<0.5.0]},{dictionary,[]},{trap_exit,true},{status,running},{heap_size,233},{stack_size,23},{reductions,123}],[]]} {error_logger,{{2010,5,28},{23,28,56}},std_info,[{application,kernel},{exited,{shutdown,{kernel,start,[normal,[]]}}},{type,permanent}]} {"Kernel pid terminated",application_controller,"{application_start_failure,kernel,{shutdown,{kernel,start,[normal,[]]}}}"} Crash dump was written to: erl_crash.dump Kernel pid terminated (application_controller) ({application_start_failure,kernel,{shutdown,{kernel,start,[normal,[]]}}}) root@domU-12-31-39-0F-7D-14:/var/lib/ejabberd# cat /var/log/ejabberd/ejabberd.log =INFO REPORT==== 2010-05-28 22:48:53 === I(<0.321.0:mod_pubsub:154) : pubsub init "localhost" [{access_createnode, pubsub_createnode}, {plugins, ["default","pep"]}] =INFO REPORT==== 2010-05-28 22:48:53 === I(<0.321.0:mod_pubsub:210) : ** tree plugin is nodetree_default =INFO REPORT==== 2010-05-28 22:48:53 === I(<0.321.0:mod_pubsub:214) : ** init default plugin =INFO REPORT==== 2010-05-28 22:48:53 === I(<0.321.0:mod_pubsub:214) : ** init pep plugin =ERROR REPORT==== 2010-05-28 23:40:08 === ** Connection attempt from disallowed node 'ejabberdctl1275090008486951000@domU-12-31-39-0F-7D-14' ** =ERROR REPORT==== 2010-05-28 23:41:10 === ** Connection attempt from disallowed node 'ejabberdctl1275090070163253000@domU-12-31-39-0F-7D-14' **

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  • Can't install ErlyBird on Netbeans 6.8

    - by Jonas
    I would like to use ErlyBird, so I downloaded the latest Netbeans (6.8), and then downloaded and unzipped ErlyBird. After that I imported the plugins in Netbeans, but during installation I was prompted with: Warning - could not install some modules: Erlang Project - The module named org.netbeans.modules.parsing.api was needed and not found. Erlang Editor - The module named org.netbeans.modules.parsing.api was needed and not found. Another module could not be installed due to the above problems. Is there a workaround to this?

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  • Calling a Add-in function from Excel's VBA

    - by graham
    I am using an Excel Add-in for an Erlangs: http://abstractmicro.com/erlang/helppages/ref-erlbblockage.htm I try to call the Erlang-B function within the Add-in from within VBA thus: Function Erl(Erlangs As Double, Capacity As Double) Erl = Application.WorksheetFunction.ErlbBlockage(Capacity, Erlangs) End Function ...but it doesn't work. I get #VALUE! returned in the Excel cell. I think it is because the function is not part of standard Excel (it is in the Add-in). So how do I call it?

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  • Learn Many Languages

    - by Jeff Foster
    My previous blog, Deliberate Practice, discussed the need for developers to “sharpen their pencil” continually, by setting aside time to learn how to tackle problems in different ways. However, the Sapir-Whorf hypothesis, a contested and somewhat-controversial concept from language theory, seems to hold reasonably true when applied to programming languages. It states that: “The structure of a language affects the ways in which its speakers conceptualize their world.” If you’re constrained by a single programming language, the one that dominates your day job, then you only have the tools of that language at your disposal to think about and solve a problem. For example, if you’ve only ever worked with Java, you would never think of passing a function to a method. A good developer needs to learn many languages. You may never deploy them in production, you may never ship code with them, but by learning a new language, you’ll have new ideas that will transfer to your current “day-job” language. With the abundant choices in programming languages, how does one choose which to learn? Alan Perlis sums it up best. “A language that doesn‘t affect the way you think about programming is not worth knowing“ With that in mind, here’s a selection of languages that I think are worth learning and that have certainly changed the way I think about tackling programming problems. Clojure Clojure is a Lisp-based language running on the Java Virtual Machine. The unique property of Lisp is homoiconicity, which means that a Lisp program is a Lisp data structure, and vice-versa. Since we can treat Lisp programs as Lisp data structures, we can write our code generation in the same style as our code. This gives Lisp a uniquely powerful macro system, and makes it ideal for implementing domain specific languages. Clojure also makes software transactional memory a first-class citizen, giving us a new approach to concurrency and dealing with the problems of shared state. Haskell Haskell is a strongly typed, functional programming language. Haskell’s type system is far richer than C# or Java, and allows us to push more of our application logic to compile-time safety. If it compiles, it usually works! Haskell is also a lazy language – we can work with infinite data structures. For example, in a board game we can generate the complete game tree, even if there are billions of possibilities, because the values are computed only as they are needed. Erlang Erlang is a functional language with a strong emphasis on reliability. Erlang’s approach to concurrency uses message passing instead of shared variables, with strong support from both the language itself and the virtual machine. Processes are extremely lightweight, and garbage collection doesn’t require all processes to be paused at the same time, making it feasible for a single program to use millions of processes at once, all without the mental overhead of managing shared state. The Benefits of Multilingualism By studying new languages, even if you won’t ever get the chance to use them in production, you will find yourself open to new ideas and ways of coding in your main language. For example, studying Haskell has taught me that you can do so much more with types and has changed my programming style in C#. A type represents some state a program should have, and a type should not be able to represent an invalid state. I often find myself refactoring methods like this… void SomeMethod(bool doThis, bool doThat) { if (!(doThis ^ doThat)) throw new ArgumentException(“At least one arg should be true”); if (doThis) DoThis(); if (doThat) DoThat(); } …into a type-based solution, like this: enum Action { DoThis, DoThat, Both }; void SomeMethod(Action action) { if (action == Action.DoThis || action == Action.Both) DoThis(); if (action == Action.DoThat || action == Action.Both) DoThat(); } At this point, I’ve removed the runtime exception in favor of a compile-time check. This is a trivial example, but is just one of many ideas that I’ve taken from one language and implemented in another.

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  • Maximizing TCP connections on HAProxy load balancer

    - by imaginative
    I am currently using HAProxy in order to load balance tcp connections from clients to my Erlang app server. The connection is persistent, which means I'm limited to roughly 64K clients on an optimized server (I'm currently running HAProxy on an m1.large EC2 instance). My app server is designed to horizontally scale based on the number of TCP connections. What's worrying me though is I'll need an equal number of HAProxy servers as app servers since it's a 1:1 connection. Is there currently a way to "proxy" the tcp connection to the app server so that once HAProxy sends the client off to my Erlang server, it can free up the connection, ready to serve another client? Are there any papers, existing solutions out there I can read so that I only have to worry about the 64K limit on my app servers, and not on the load balancing servers themselves?

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  • Advice for a computer science sophomore in college?

    - by RDas
    Hi Everyone! I'm a sophomore in college majoring in Computer Science and Math. I have always loved programming. I started programming in C when I was nine years old and over the years I've picked up Visual Basic, C#, Java, C++, JavaScript, Objective-C, Python, Ruby, elementary Haskell and elementary Erlang, and I learned Perl back in the day which I've mostly forgotten. I have not done much network programming. I have done CGI programming, but that was about six/seven years ago. I've done some socket programming and written (school) programs to do interprocess communication, which I understood and liked. I'm taking a course on client/server programming and another one on network security next semester, which I am really looking forward to. I'm seeking advice on how to proceed with future learning. I've mostly done application (mobile and desktop) development, not much of web development. I'd like to pick up some web development this coming semester. Since I know Ruby and Python, should I start by learning Django and/or Rails? Any other suggestions on starting web development? I have a good understanding of HTML and CSS. Also, I'd also like to know how hard it is to pick up and be good (read: productive) in functional programming languages coming from a purely structured/object oriented background? I've been reading up on Erlang and Haskell, and I'd like to know your opinions on whether it's worth my time trying to learn them. What about Lisp, Scheme and other functional languages? Any help/ideas would be really appreciated.

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  • Scala actors: receive vs react

    - by jqno
    Let me first say that I have quite a lot of Java experience, but have only recently become interested in functional languages. Recently I've started looking at Scala, which seems like a very nice language. However, I've been reading about Scala's Actor framework in Programming in Scala, and there's one thing I don't understand. In chapter 30.4 it says that using react instead of receive makes it possible to re-use threads, which is good for performance, since threads are expensive in the JVM. Does this mean that, as long as I remember to call react instead of receive, I can start as many Actors as I like? Before discovering Scala, I've been playing with Erlang, and the author of Programming Erlang boasts about spawning over 200,000 processes without breaking a sweat. I'd hate to do that with Java threads. What kind of limits am I looking at in Scala as compared to Erlang (and Java)? Also, how does this thread re-use work in Scala? Let's assume, for simplicity, that I have only one thread. Will all the actors that I start run sequentially in this thread, or will some sort of task-switching take place? For example, if I start two actors that ping-pong messages to each other, will I risk deadlock if they're started in the same thread? According to Programming in Scala, writing actors to use react is more difficult than with receive. This sounds plausible, since react doesn't return. However, the book goes on to show how you can put a react inside a loop using Actor.loop. As a result, you get loop { react { ... } } which, to me, seems pretty similar to while (true) { receive { ... } } which is used earlier in the book. Still, the book says that "in practice, programs will need at least a few receive's". So what am I missing here? What can receive do that react cannot, besides return? And why do I care? Finally, coming to the core of what I don't understand: the book keeps mentioning how using react makes it possible to discard the call stack to re-use the thread. How does that work? Why is it necessary to discard the call stack? And why can the call stack be discarded when a function terminates by throwing an exception (react), but not when it terminates by returning (receive)? I have the impression that Programming in Scala has been glossing over some of the key issues here, which is a shame, because otherwise it's a truly excellent book.

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  • Are there any purely functional Schemes or Lisps?

    - by nickname
    Over the past few months, I've put a lot of effort into learning (or attempting to learn) several functional programming languages. I really like math, so they have been very natural for me to use. Simply to be more specific, I have tried Common Lisp, Scheme, Haskell, OCaml, and (a little bit of) Erlang. I did not like the syntax of OCaml and do not have enough Erlang knowledge to make a judgment on it yet. Because of its consistent and beautiful (non-)syntax, I really like Scheme. However, I really do appreciate the stateless nature of purely functional programming languages such as Haskell. Haskell looks very interesting, but the amount of inconsistent and non-extendable syntax really bothered me. In the interest of preventing a Lisp vs Haskell flame war, just pretend that I can't use Haskell for some other reason. Therefore, my question is: Are there any purely functional Schemes (or Lisps in general)?

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  • Riak "error":"insufficient_vnodes_available"

    - by Wolfiem
    We have 4 nodes Riak installation. They are running on Ubuntu 12.04 LTS Precise installed servers. We have installed 1.1.4 at August 1st 2012 and upgraded 1.2.0 when its available. Server names are: f1 - 10.10.0.12 - This is the first installed server. We have joined other ones to this server. This also serves Riak control. s2 - 10.10.0.22 - s3 - 10.10.0.23 - s4 - 10.10.0.24 - This server also serves Riak control. This morning we've seen "insufficient nodes available" error at our applications log and restarted all nodes. 3 of them became available except "f1" UPDATE : while I prepare this message live 3 nodes became unavailable and need restart Riak. wolfiem@f01:~$ sudo /etc/init.d/riak start Riak failed to start within 15 seconds, see the output of 'riak console' for more information. If you want to wait longer, set the environment variable WAIT_FOR_ERLANG to the number of seconds to wait. I've tried to set WAIT_FOR_ERLANG value to 60 seconds but I can't. adding this line in vm.args didn't work: -env WAIT_FOR_ERLANG 60 I also tried to set this from terminal but it didn't work either. wolfiem@f01:~$ export WAIT_FOR_ERLANG=60 It still says "Riak failed to start within 15 seconds" This is the console.log output: 2012-09-11 10:58:02.532 [info] <0.7.0> Application lager started on node '[email protected]' 2012-09-11 10:58:02.560 [warning] <0.148.0>@riak_core_ring_manager:reload_ring:231 No ring file available. 2012-09-11 10:58:02.585 [error] <0.164.0> CRASH REPORT Process <0.164.0> with 0 neighbours exited with reason: eaddrnotavail in gen_server:init_it/6 line 320 This is the error.log output 2012-09-11 10:58:02.585 [error] <0.164.0> CRASH REPORT Process <0.164.0> with 0 neighbours exited with reason: eaddrnotavail in gen_server:init_it/6 line 320 This is the crash.log output: 2012-09-11 10:58:02 =CRASH REPORT==== crasher: initial call: mochiweb_socket_server:init/1 pid: <0.164.0> registered_name: [] exception exit: {eaddrnotavail,[{gen_server,init_it,6,[{file,"gen_server.erl"},{line,320}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,227}]}]} ancestors: [riak_core_sup,<0.135.0>] messages: [] links: [<0.136.0>] dictionary: [] trap_exit: true status: running heap_size: 377 stack_size: 24 reductions: 403 neighbours: You can find the riak console output below: wolfiem@f01:~$ riak console Attempting to restart script through sudo -H -u riak Exec: /usr/lib/riak/erts-5.9.1/bin/erlexec -boot /usr/lib/riak/releases/1.2.0/riak -embedded -config /etc/riak/app.config -pa /usr/lib/riak/basho-patches -args_file /etc/riak/vm.args -- console Root: /usr/lib/riak Erlang R15B01 (erts-5.9.1) [source] [64-bit] [smp:8:8] [async-threads:64] [kernel-poll:true] =INFO REPORT==== 11-Sep-2012::10:44:18 === alarm_handler: {set,{system_memory_high_watermark,[]}} ** /usr/lib/riak/lib/observer-1.1/ebin/etop_txt.beam hides /usr/lib/riak/lib/basho-patches/etop_txt.beam ** Found 1 name clashes in code paths 10:44:19.099 [info] Application lager started on node '[email protected]' 10:44:19.130 [warning] No ring file available. 10:44:19.158 [error] CRASH REPORT Process <0.164.0> with 0 neighbours exited with reason: eaddrnotavail in gen_server:init_it/6 line 320 /usr/lib/riak/lib/os_mon-2.2.9/priv/bin/memsup: Erlang has closed. =INFO REPORT==== 11-Sep-2012::10:44:19 === alarm_handler: {clear,system_memory_high_watermark} Erlang has closed {"Kernel pid terminated",application_controller,"{application_start_failure,riak_core,{shutdown,{riak_core_app,start,[normal,[]]}}}"} Crash dump was written to: /var/log/riak/erl_crash.dump Kernel pid terminated (application_controller) ({application_start_failure,riak_core,{shutdown,{riak_core_app,start,[normal,[]]}}})

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  • Language Club

    - by Ben Griswold
    We started a language club at work this week.  Thus far, we have a collective interest in a number of languages: Python, Ruby, F#, Erlang, Objective-C, Scala, Clojure, Haskell and Go. There are more but these 9 received the most votes. During the first few meetings we are going to determine which language we should tackle first. To help make our selection, each member will provide a quick overview of their favored language by answering the following set of questions: Why are you interested in learning “your” language(s). (There’s lots of work, I’m an MS shill, It’s hip and  fun, etc) What type of language is it?  (OO, dynamic, functional, procedural, declarative, etc) What types of problems is your language best suited to solve?  (Algorithms over big data, rapid application development, modeling, merely academic, etc) Can you provide examples of where/how it is being used?  If it isn’t being used, why not?  (Erlang was invented at Ericsson to provide an extremely fault tolerant, concurrent system.) Quick history – Who created/sponsored the language?  When was it created?  Is it currently active? Does the language have hardware support (an attempt was made at one point to create processor instruction sets specific to Prolog), or can it run as an interpreted language inside another language (like Ruby in the JVM)? Are there facilities for programs written in this language to communicate with other languages?  How does this affect its utility? Does the language have a IDE tool support?  (Think Eclipse or Visual Studio) How well is the language supported in terms of books, community and documentation? What’s the number one things which differentiates the language from others?  (i.e. Why is it cool?) How is the language applicability to us as consultants?  What would the impact be of using the language in terms of cost, maintainability, personnel costs, etc.? What’s the number one things which differentiates the language from others?  (i.e. Why is it cool?) This should provide an decent introduction into nearly a dozen languages and give us enough context to decide which single language deserves our undivided attention for the weeks to come.  Stay tuned for the winner…

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  • My blog has now moved to http://dataidol.com/tonyrogerson

    - by tonyrogerson
    I've decided to implement a new blogging infrastructure based on WordPress; the community server stuff I'm using has got a bit tired and WordPress offers a wealth of plug-ins to do pretty much everything I want.So, see http://dataidol.com/tonyrogerson for my new blog; its not just a move, I have broadened my coverage to encompass all things data, the first couple of posts talk about Short-Stroking hard disks (something I've presented on a number of times now), I've also got some Erlang content.Anyway, enjoy!T

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  • Why was Scala not implemented with C or C++

    - by jpartogi
    Does anybody know why was Scala implemented in Java and .NET instead of C or C++? Most languages are implemented with Cor C++ [i.e Erlang, Python, PHP, Ruby, Perl]. What are the advantages for Scala implemented in Java and .NET other than giving access to Java and .NET libraries? UPDATE Woudln't Scala gain more benefit if it is implemented in C because it can be tuned better rather than relying on JVM?

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  • Red Gate Coder interviews: Alex Davies

    - by Michael Williamson
    Alex Davies has been a software engineer at Red Gate since graduating from university, and is currently busy working on .NET Demon. We talked about tackling parallel programming with his actors framework, a scientific approach to debugging, and how JavaScript is going to affect the programming languages we use in years to come. So, if we start at the start, how did you get started in programming? When I was seven or eight, I was given a BBC Micro for Christmas. I had asked for a Game Boy, but my dad thought it would be better to give me a proper computer. For a year or so, I only played games on it, but then I found the user guide for writing programs in it. I gradually started doing more stuff on it and found it fun. I liked creating. As I went into senior school I continued to write stuff on there, trying to write games that weren’t very good. I got a real computer when I was fourteen and found ways to write BASIC on it. Visual Basic to start with, and then something more interesting than that. How did you learn to program? Was there someone helping you out? Absolutely not! I learnt out of a book, or by experimenting. I remember the first time I found a loop, I was like “Oh my God! I don’t have to write out the same line over and over and over again any more. It’s amazing!” When did you think this might be something that you actually wanted to do as a career? For a long time, I thought it wasn’t something that you would do as a career, because it was too much fun to be a career. I thought I’d do chemistry at university and some kind of career based on chemical engineering. And then I went to a careers fair at school when I was seventeen or eighteen, and it just didn’t interest me whatsoever. I thought “I could be a programmer, and there’s loads of money there, and I’m good at it, and it’s fun”, but also that I shouldn’t spoil my hobby. Now I don’t really program in my spare time any more, which is a bit of a shame, but I program all the rest of the time, so I can live with it. Do you think you learnt much about programming at university? Yes, definitely! I went into university knowing how to make computers do anything I wanted them to do. However, I didn’t have the language to talk about algorithms, so the algorithms course in my first year was massively important. Learning other language paradigms like functional programming was really good for breadth of understanding. Functional programming influences normal programming through design rather than actually using it all the time. I draw inspiration from it to write imperative programs which I think is actually becoming really fashionable now, but I’ve been doing it for ages. I did it first! There were also some courses on really odd programming languages, a bit of Prolog, a little bit of C. Having a little bit of each of those is something that I would have never done on my own, so it was important. And then there are knowledge-based courses which are about not programming itself but things that have been programmed like TCP. Those are really important for examples for how to approach things. Did you do any internships while you were at university? Yeah, I spent both of my summers at the same company. I thought I could code well before I went there. Looking back at the crap that I produced, it was only surpassed in its crappiness by all of the other code already in that company. I’m so much better at writing nice code now than I used to be back then. Was there just not a culture of looking after your code? There was, they just didn’t hire people for their abilities in that area. They hired people for raw IQ. The first indicator of it going wrong was that they didn’t have any computer scientists, which is a bit odd in a programming company. But even beyond that they didn’t have people who learnt architecture from anyone else. Most of them had started straight out of university, so never really had experience or mentors to learn from. There wasn’t the experience to draw from to teach each other. In the second half of my second internship, I was being given tasks like looking at new technologies and teaching people stuff. Interns shouldn’t be teaching people how to do their jobs! All interns are going to have little nuggets of things that you don’t know about, but they shouldn’t consistently be the ones who know the most. It’s not a good environment to learn. I was going to ask how you found working with people who were more experienced than you… When I reached Red Gate, I found some people who were more experienced programmers than me, and that was difficult. I’ve been coding since I was tiny. At university there were people who were cleverer than me, but there weren’t very many who were more experienced programmers than me. During my internship, I didn’t find anyone who I classed as being a noticeably more experienced programmer than me. So, it was a shock to the system to have valid criticisms rather than just formatting criticisms. However, Red Gate’s not so big on the actual code review, at least it wasn’t when I started. We did an entire product release and then somebody looked over all of the UI of that product which I’d written and say what they didn’t like. By that point, it was way too late and I’d disagree with them. Do you think the lack of code reviews was a bad thing? I think if there’s going to be any oversight of new people, then it should be continuous rather than chunky. For me I don’t mind too much, I could go out and get oversight if I wanted it, and in those situations I felt comfortable without it. If I was managing the new person, then maybe I’d be keener on oversight and then the right way to do it is continuously and in very, very small chunks. Have you had any significant projects you’ve worked on outside of a job? When I was a teenager I wrote all sorts of stuff. I used to write games, I derived how to do isomorphic projections myself once. I didn’t know what the word was so I couldn’t Google for it, so I worked it out myself. It was horrifically complicated. But it sort of tailed off when I started at university, and is now basically zero. If I do side-projects now, they tend to be work-related side projects like my actors framework, NAct, which I started in a down tools week. Could you explain a little more about NAct? It is a little C# framework for writing parallel code more easily. Parallel programming is difficult when you need to write to shared data. Sometimes parallel programming is easy because you don’t need to write to shared data. When you do need to access shared data, you could just have your threads pile in and do their work, but then you would screw up the data because the threads would trample on each other’s toes. You could lock, but locks are really dangerous if you’re using more than one of them. You get interactions like deadlocks, and that’s just nasty. Actors instead allows you to say this piece of data belongs to this thread of execution, and nobody else can read it. If you want to read it, then ask that thread of execution for a piece of it by sending a message, and it will send the data back by a message. And that avoids deadlocks as long as you follow some obvious rules about not making your actors sit around waiting for other actors to do something. There are lots of ways to write actors, NAct allows you to do it as if it was method calls on other objects, which means you get all the strong type-safety that C# programmers like. Do you think that this is suitable for the majority of parallel programming, or do you think it’s only suitable for specific cases? It’s suitable for most difficult parallel programming. If you’ve just got a hundred web requests which are all independent of each other, then I wouldn’t bother because it’s easier to just spin them up in separate threads and they can proceed independently of each other. But where you’ve got difficult parallel programming, where you’ve got multiple threads accessing multiple bits of data in multiple ways at different times, then actors is at least as good as all other ways, and is, I reckon, easier to think about. When you’re using actors, you presumably still have to write your code in a different way from you would otherwise using single-threaded code. You can’t use actors with any methods that have return types, because you’re not allowed to call into another actor and wait for it. If you want to get a piece of data out of another actor, then you’ve got to use tasks so that you can use “async” and “await” to await asynchronously for it. But other than that, you can still stick things in classes so it’s not too different really. Rather than having thousands of objects with mutable state, you can use component-orientated design, where there are only a few mutable classes which each have a small number of instances. Then there can be thousands of immutable objects. If you tend to do that anyway, then actors isn’t much of a jump. If I’ve already built my system without any parallelism, how hard is it to add actors to exploit all eight cores on my desktop? Usually pretty easy. If you can identify even one boundary where things look like messages and you have components where some objects live on one side and these other objects live on the other side, then you can have a granddaddy object on one side be an actor and it will parallelise as it goes across that boundary. Not too difficult. If we do get 1000-core desktop PCs, do you think actors will scale up? It’s hard. There are always in the order of twenty to fifty actors in my whole program because I tend to write each component as actors, and I tend to have one instance of each component. So this won’t scale to a thousand cores. What you can do is write data structures out of actors. I use dictionaries all over the place, and if you need a dictionary that is going to be accessed concurrently, then you could build one of those out of actors in no time. You can use queuing to marshal requests between different slices of the dictionary which are living on different threads. So it’s like a distributed hash table but all of the chunks of it are on the same machine. That means that each of these thousand processors has cached one small piece of the dictionary. I reckon it wouldn’t be too big a leap to start doing proper parallelism. Do you think it helps if actors get baked into the language, similarly to Erlang? Erlang is excellent in that it has thread-local garbage collection. C# doesn’t, so there’s a limit to how well C# actors can possibly scale because there’s a single garbage collected heap shared between all of them. When you do a global garbage collection, you’ve got to stop all of the actors, which is seriously expensive, whereas in Erlang garbage collections happen per-actor, so they’re insanely cheap. However, Erlang deviated from all the sensible language design that people have used recently and has just come up with crazy stuff. You can definitely retrofit thread-local garbage collection to .NET, and then it’s quite well-suited to support actors, even if it’s not baked into the language. Speaking of language design, do you have a favourite programming language? I’ll choose a language which I’ve never written before. I like the idea of Scala. It sounds like C#, only with some of the niggles gone. I enjoy writing static types. It means you don’t have to writing tests so much. When you say it doesn’t have some of the niggles? C# doesn’t allow the use of a property as a method group. It doesn’t have Scala case classes, or sum types, where you can do a switch statement and the compiler checks that you’ve checked all the cases, which is really useful in functional-style programming. Pattern-matching, in other words. That’s actually the major niggle. C# is pretty good, and I’m quite happy with C#. And what about going even further with the type system to remove the need for tests to something like Haskell? Or is that a step too far? I’m quite a pragmatist, I don’t think I could deal with trying to write big systems in languages with too few other users, especially when learning how to structure things. I just don’t know anyone who can teach me, and the Internet won’t teach me. That’s the main reason I wouldn’t use it. If I turned up at a company that writes big systems in Haskell, I would have no objection to that, but I wouldn’t instigate it. What about things in C#? For instance, there’s contracts in C#, so you can try to statically verify a bit more about your code. Do you think that’s useful, or just not worthwhile? I’ve not really tried it. My hunch is that it needs to be built into the language and be quite mathematical for it to work in real life, and that doesn’t seem to have ended up true for C# contracts. I don’t think anyone who’s tried them thinks they’re any good. I might be wrong. On a slightly different note, how do you like to debug code? I think I’m quite an odd debugger. I use guesswork extremely rarely, especially if something seems quite difficult to debug. I’ve been bitten spending hours and hours on guesswork and not being scientific about debugging in the past, so now I’m scientific to a fault. What I want is to see the bug happening in the debugger, to step through the bug happening. To watch the program going from a valid state to an invalid state. When there’s a bug and I can’t work out why it’s happening, I try to find some piece of evidence which places the bug in one section of the code. From that experiment, I binary chop on the possible causes of the bug. I suppose that means binary chopping on places in the code, or binary chopping on a stage through a processing cycle. Basically, I’m very stupid about how I debug. I won’t make any guesses, I won’t use any intuition, I will only identify the experiment that’s going to binary chop most effectively and repeat rather than trying to guess anything. I suppose it’s quite top-down. Is most of the time then spent in the debugger? Absolutely, if at all possible I will never debug using print statements or logs. I don’t really hold much stock in outputting logs. If there’s any bug which can be reproduced locally, I’d rather do it in the debugger than outputting logs. And with SmartAssembly error reporting, there’s not a lot that can’t be either observed in an error report and just fixed, or reproduced locally. And in those other situations, maybe I’ll use logs. But I hate using logs. You stare at the log, trying to guess what’s going on, and that’s exactly what I don’t like doing. You have to just look at it and see does this look right or wrong. We’ve covered how you get to grip with bugs. How do you get to grips with an entire codebase? I watch it in the debugger. I find little bugs and then try to fix them, and mostly do it by watching them in the debugger and gradually getting an understanding of how the code works using my process of binary chopping. I have to do a lot of reading and watching code to choose where my slicing-in-half experiment is going to be. The last time I did it was SmartAssembly. The old code was a complete mess, but at least it did things top to bottom. There wasn’t too much of some of the big abstractions where flow of control goes all over the place, into a base class and back again. Code’s really hard to understand when that happens. So I like to choose a little bug and try to fix it, and choose a bigger bug and try to fix it. Definitely learn by doing. I want to always have an aim so that I get a little achievement after every few hours of debugging. Once I’ve learnt the codebase I might be able to fix all the bugs in an hour, but I’d rather be using them as an aim while I’m learning the codebase. If I was a maintainer of a codebase, what should I do to make it as easy as possible for you to understand? Keep distinct concepts in different places. And name your stuff so that it’s obvious which concepts live there. You shouldn’t have some variable that gets set miles up the top of somewhere, and then is read miles down to choose some later behaviour. I’m talking from a very much SmartAssembly point of view because the old SmartAssembly codebase had tons and tons of these things, where it would read some property of the code and then deal with it later. Just thousands of variables in scope. Loads of things to think about. If you can keep concepts separate, then it aids me in my process of fixing bugs one at a time, because each bug is going to more or less be understandable in the one place where it is. And what about tests? Do you think they help at all? I’ve never had the opportunity to learn a codebase which has had tests, I don’t know what it’s like! What about when you’re actually developing? How useful do you find tests in finding bugs or regressions? Finding regressions, absolutely. Running bits of code that would be quite hard to run otherwise, definitely. It doesn’t happen very often that a test finds a bug in the first place. I don’t really buy nebulous promises like tests being a good way to think about the spec of the code. My thinking goes something like “This code works at the moment, great, ship it! Ah, there’s a way that this code doesn’t work. Okay, write a test, demonstrate that it doesn’t work, fix it, use the test to demonstrate that it’s now fixed, and keep the test for future regressions.” The most valuable tests are for bugs that have actually happened at some point, because bugs that have actually happened at some point, despite the fact that you think you’ve fixed them, are way more likely to appear again than new bugs are. Does that mean that when you write your code the first time, there are no tests? Often. The chance of there being a bug in a new feature is relatively unaffected by whether I’ve written a test for that new feature because I’m not good enough at writing tests to think of bugs that I would have written into the code. So not writing regression tests for all of your code hasn’t affected you too badly? There are different kinds of features. Some of them just always work, and are just not flaky, they just continue working whatever you throw at them. Maybe because the type-checker is particularly effective around them. Writing tests for those features which just tend to always work is a waste of time. And because it’s a waste of time I’ll tend to wait until a feature has demonstrated its flakiness by having bugs in it before I start trying to test it. You can get a feel for whether it’s going to be flaky code as you’re writing it. I try to write it to make it not flaky, but there are some things that are just inherently flaky. And very occasionally, I’ll think “this is going to be flaky” as I’m writing, and then maybe do a test, but not most of the time. How do you think your programming style has changed over time? I’ve got clearer about what the right way of doing things is. I used to flip-flop a lot between different ideas. Five years ago I came up with some really good ideas and some really terrible ideas. All of them seemed great when I thought of them, but they were quite diverse ideas, whereas now I have a smaller set of reliable ideas that are actually good for structuring code. So my code is probably more similar to itself than it used to be back in the day, when I was trying stuff out. I’ve got more disciplined about encapsulation, I think. There are operational things like I use actors more now than I used to, and that forces me to use immutability more than I used to. The first code that I wrote in Red Gate was the memory profiler UI, and that was an actor, I just didn’t know the name of it at the time. I don’t really use object-orientation. By object-orientation, I mean having n objects of the same type which are mutable. I want a constant number of objects that are mutable, and they should be different types. I stick stuff in dictionaries and then have one thing that owns the dictionary and puts stuff in and out of it. That’s definitely a pattern that I’ve seen recently. I think maybe I’m doing functional programming. Possibly. It’s plausible. If you had to summarise the essence of programming in a pithy sentence, how would you do it? Programming is the form of art that, without losing any of the beauty of architecture or fine art, allows you to produce things that people love and you make money from. So you think it’s an art rather than a science? It’s a little bit of engineering, a smidgeon of maths, but it’s not science. Like architecture, programming is on that boundary between art and engineering. If you want to do it really nicely, it’s mostly art. You can get away with doing architecture and programming entirely by having a good engineering mind, but you’re not going to produce anything nice. You’re not going to have joy doing it if you’re an engineering mind. Architects who are just engineering minds are not going to enjoy their job. I suppose engineering is the foundation on which you build the art. Exactly. How do you think programming is going to change over the next ten years? There will be an unfortunate shift towards dynamically-typed languages, because of JavaScript. JavaScript has an unfair advantage. JavaScript’s unfair advantage will cause more people to be exposed to dynamically-typed languages, which means other dynamically-typed languages crop up and the best features go into dynamically-typed languages. Then people conflate the good features with the fact that it’s dynamically-typed, and more investment goes into dynamically-typed languages. They end up better, so people use them. What about the idea of compiling other languages, possibly statically-typed, to JavaScript? It’s a reasonable idea. I would like to do it, but I don’t think enough people in the world are going to do it to make it pick up. The hordes of beginners are the lifeblood of a language community. They are what makes there be good tools and what makes there be vibrant community websites. And any particular thing which is the same as JavaScript only with extra stuff added to it, although it might be technically great, is not going to have the hordes of beginners. JavaScript is always to be quickest and easiest way for a beginner to start programming in the browser. And dynamically-typed languages are great for beginners. Compilers are pretty scary and beginners don’t write big code. And having your errors come up in the same place, whether they’re statically checkable errors or not, is quite nice for a beginner. If someone asked me to teach them some programming, I’d teach them JavaScript. If dynamically-typed languages are great for beginners, when do you think the benefits of static typing start to kick in? The value of having a statically typed program is in the tools that rely on the static types to produce a smooth IDE experience rather than actually telling me my compile errors. And only once you’re experienced enough a programmer that having a really smooth IDE experience makes a blind bit of difference, does static typing make a blind bit of difference. So it’s not really about size of codebase. If I go and write up a tiny program, I’m still going to get value out of writing it in C# using ReSharper because I’m experienced with C# and ReSharper enough to be able to write code five times faster if I have that help. Any other visions of the future? Nobody’s going to use actors. Because everyone’s going to be running on single-core VMs connected over network-ready protocols like JSON over HTTP. So, parallelism within one operating system is going to die. But until then, you should use actors. More Red Gater Coder interviews

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