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• mysqld crashes on any statement

  - by ??iu

  I restarted my slave to change configuration settings to skip reverse hostname lookup on connecting and to enable the slow query log. I edited /etc/my.cnf making only these changes, then restarted mysqld with /etc/init.d/mysql restart All appeared to be well but when I connect to msyqld remotely or locally though it connects okay a slight problem is that mysqld crashes whenever you try to issue any kind of statement. The client looks like: Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 3 Server version: 5.1.31-1ubuntu2-log Type 'help;' or '\h' for help. Type '\c' to clear the buffer. mysql> show tables; ERROR 2006 (HY000): MySQL server has gone away No connection. Trying to reconnect... Connection id: 1 Current database: mydb ERROR 2006 (HY000): MySQL server has gone away No connection. Trying to reconnect... ERROR 2003 (HY000): Can't connect to MySQL server on 'xx.xx.xx.xx' (61) ERROR: Can't connect to the server ERROR 2006 (HY000): MySQL server has gone away No connection. Trying to reconnect... ERROR 2003 (HY000): Can't connect to MySQL server on 'xx.xx.xx.xx' (61) ERROR: Can't connect to the server ERROR 2006 (HY000): MySQL server has gone away Bus error The mysqld error log looks like: 101210 16:35:51 InnoDB: Error: (1500) Couldn't read the MAX(job_id) autoinc value from the index (PRIMARY). 101210 16:35:51 InnoDB: Assertion failure in thread 140245598570832 in file handler/ha_innodb.cc line 2595 InnoDB: Failing assertion: error == DB_SUCCESS InnoDB: We intentionally generate a memory trap. InnoDB: Submit a detailed bug report to http://bugs.mysql.com. InnoDB: If you get repeated assertion failures or crashes, even InnoDB: immediately after the mysqld startup, there may be InnoDB: corruption in the InnoDB tablespace. Please refer to InnoDB: http://dev.mysql.com/doc/refman/5.1/en/forcing-recovery.html InnoDB: about forcing recovery. 101210 16:35:51 - mysqld got signal 6 ; This could be because you hit a bug. It is also possible that this binary or one of the libraries it was linked against is corrupt, improperly built, or misconfigured. This error can also be caused by malfunctioning hardware. We will try our best to scrape up some info that will hopefully help diagnose the problem, but since we have already crashed, something is definitely wrong and this may fail. key_buffer_size=16777216 read_buffer_size=131072 max_used_connections=3 max_threads=600 threads_connected=3 It is possible that mysqld could use up to key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 1328077 K bytes of memory Hope that's ok; if not, decrease some variables in the equation. thd: 0x18209220 Attempting backtrace. You can use the following information to find out where mysqld died. If you see no messages after this, something went terribly wrong... stack_bottom = 0x7f8d791580d0 thread_stack 0x20000 /usr/sbin/mysqld(my_print_stacktrace+0x29) [0x8b4f89] /usr/sbin/mysqld(handle_segfault+0x383) [0x5f8f03] /lib/libpthread.so.0 [0x7f902a76a080] /lib/libc.so.6(gsignal+0x35) [0x7f90291f8fb5] /lib/libc.so.6(abort+0x183) [0x7f90291fabc3] /usr/sbin/mysqld(ha_innobase::open(char const*, int, unsigned int)+0x41b) [0x781f4b] /usr/sbin/mysqld(handler::ha_open(st_table*, char const*, int, int)+0x3f) [0x6db00f] /usr/sbin/mysqld(open_table_from_share(THD*, st_table_share*, char const*, unsigned int, unsigned int, unsigned int, st_table*, bool)+0x57a) [0x64760a] /usr/sbin/mysqld [0x63f281] /usr/sbin/mysqld(open_table(THD*, TABLE_LIST*, st_mem_root*, bool*, unsigned int)+0x626) [0x641e16] /usr/sbin/mysqld(open_tables(THD*, TABLE_LIST**, unsigned int*, unsigned int)+0x5db) [0x6429cb] /usr/sbin/mysqld(open_normal_and_derived_tables(THD*, TABLE_LIST*, unsigned int)+0x1e) [0x642b0e] /usr/sbin/mysqld(mysqld_list_fields(THD*, TABLE_LIST*, char const*)+0x22) [0x70b292] /usr/sbin/mysqld(dispatch_command(enum_server_command, THD*, char*, unsigned int)+0x146d) [0x60dc1d] /usr/sbin/mysqld(do_command(THD*)+0xe8) [0x60dda8] /usr/sbin/mysqld(handle_one_connection+0x226) [0x601426] /lib/libpthread.so.0 [0x7f902a7623ba] /lib/libc.so.6(clone+0x6d) [0x7f90292abfcd] Trying to get some variables. Some pointers may be invalid and cause the dump to abort... thd->query at 0x18213c70 = thd->thread_id=3 thd->killed=NOT_KILLED The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains information that should help you find out what is causing the crash. 101210 16:35:51 mysqld_safe Number of processes running now: 0 101210 16:35:51 mysqld_safe mysqld restarted InnoDB: The log sequence number in ibdata files does not match InnoDB: the log sequence number in the ib_logfiles! 101210 16:35:54 InnoDB: Database was not shut down normally! InnoDB: Starting crash recovery. InnoDB: Reading tablespace information from the .ibd files... InnoDB: Restoring possible half-written data pages from the doublewrite InnoDB: buffer... 101210 16:35:56 InnoDB: Started; log sequence number 456 143528628 101210 16:35:56 [Warning] 'user' entry 'root@PSDB102' ignored in --skip-name-resolve mode. 101210 16:35:56 [Warning] Neither --relay-log nor --relay-log-index were used; so replication may break when this MySQL server acts as a slave and has his hostname changed!! Please use '--relay-log=mysqld-relay-bin' to avoid this problem. 101210 16:35:56 [Note] Event Scheduler: Loaded 0 events 101210 16:35:56 [Note] /usr/sbin/mysqld: ready for connections. Version: '5.1.31-1ubuntu2-log' socket: '/var/run/mysqld/mysqld.sock' port: 3306 (Ubuntu) 101210 16:36:11 InnoDB: Error: (1500) Couldn't read the MAX(job_id) autoinc value from the index (PRIMARY). 101210 16:36:11 InnoDB: Assertion failure in thread 139955151501648 in file handler/ha_innodb.cc line 2595 InnoDB: Failing assertion: error == DB_SUCCESS InnoDB: We intentionally generate a memory trap. InnoDB: Submit a detailed bug report to http://bugs.mysql.com. InnoDB: If you get repeated assertion failures or crashes, even InnoDB: immediately after the mysqld startup, there may be InnoDB: corruption in the InnoDB tablespace. Please refer to InnoDB: http://dev.mysql.com/doc/refman/5.1/en/forcing-recovery.html InnoDB: about forcing recovery. 101210 16:36:11 - mysqld got signal 6 ; This could be because you hit a bug. It is also possible that this binary or one of the libraries it was linked against is corrupt, improperly built, or misconfigured. This error can also be caused by malfunctioning hardware. We will try our best to scrape up some info that will hopefully help diagnose the problem, but since we have already crashed, something is definitely wrong and this may fail. key_buffer_size=16777216 read_buffer_size=131072 max_used_connections=1 max_threads=600 threads_connected=1 It is possible that mysqld could use up to key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 1328077 K bytes of memory Hope that's ok; if not, decrease some variables in the equation. thd: 0x18588720 Attempting backtrace. You can use the following information to find out where mysqld died. If you see no messages after this, something went terribly wrong... stack_bottom = 0x7f49d916f0d0 thread_stack 0x20000 /usr/sbin/mysqld(my_print_stacktrace+0x29) [0x8b4f89] /usr/sbin/mysqld(handle_segfault+0x383) [0x5f8f03] /lib/libpthread.so.0 [0x7f4c8a73f080] /lib/libc.so.6(gsignal+0x35) [0x7f4c891cdfb5] /lib/libc.so.6(abort+0x183) [0x7f4c891cfbc3] /usr/sbin/mysqld(ha_innobase::open(char const*, int, unsigned int)+0x41b) [0x781f4b] /usr/sbin/mysqld(handler::ha_open(st_table*, char const*, int, int)+0x3f) [0x6db00f] /usr/sbin/mysqld(open_table_from_share(THD*, st_table_share*, char const*, unsigned int, unsigned int, unsigned int, st_table*, bool)+0x57a) [0x64760a] /usr/sbin/mysqld [0x63f281] /usr/sbin/mysqld(open_table(THD*, TABLE_LIST*, st_mem_root*, bool*, unsigned int)+0x626) [0x641e16] /usr/sbin/mysqld(open_tables(THD*, TABLE_LIST**, unsigned int*, unsigned int)+0x5db) [0x6429cb] /usr/sbin/mysqld(open_normal_and_derived_tables(THD*, TABLE_LIST*, unsigned int)+0x1e) [0x642b0e] /usr/sbin/mysqld(mysqld_list_fields(THD*, TABLE_LIST*, char const*)+0x22) [0x70b292] /usr/sbin/mysqld(dispatch_command(enum_server_command, THD*, char*, unsigned int)+0x146d) [0x60dc1d] /usr/sbin/mysqld(do_command(THD*)+0xe8) [0x60dda8] /usr/sbin/mysqld(handle_one_connection+0x226) [0x601426] /lib/libpthread.so.0 [0x7f4c8a7373ba] /lib/libc.so.6(clone+0x6d) [0x7f4c89280fcd] Trying to get some variables. Some pointers may be invalid and cause the dump to abort... thd->query at 0x18599950 = thd->thread_id=1 thd->killed=NOT_KILLED The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains information that should help you find out what is causing the crash. 101210 16:36:11 mysqld_safe Number of processes running now: 0 101210 16:36:11 mysqld_safe mysqld restarted The config is [mysqld_safe] socket = /var/run/mysqld/mysqld.sock nice = 0 [mysqld] innodb_file_per_table innodb_buffer_pool_size=10G innodb_log_buffer_size=4M innodb_flush_log_at_trx_commit=2 innodb_thread_concurrency=8 skip-slave-start server-id=3 # # * IMPORTANT # If you make changes to these settings and your system uses apparmor, you may # also need to also adjust /etc/apparmor.d/usr.sbin.mysqld. # user = mysql pid-file = /var/run/mysqld/mysqld.pid socket = /var/run/mysqld/mysqld.sock port = 3306 basedir = /usr datadir = /DB2/mysql tmpdir = /tmp skip-external-locking # # Instead of skip-networking the default is now to listen only on # localhost which is more compatible and is not less secure. #bind-address = 127.0.0.1 # # * Fine Tuning # key_buffer = 16M max_allowed_packet = 16M thread_stack = 128K thread_cache_size = 8 # This replaces the startup script and checks MyISAM tables if needed # the first time they are touched myisam-recover = BACKUP max_connections = 600 #table_cache = 64 #thread_concurrency = 10 # # * Query Cache Configuration # query_cache_limit = 1M query_cache_size = 32M # skip-federated slow-query-log skip-name-resolve Update: I followed the instructions as per http://dev.mysql.com/doc/refman/5.1/en/forcing-innodb-recovery.html and set innodb_force_recovery = 4 and the logs are showing a different error but the behavior is still the same: 101210 19:14:15 mysqld_safe mysqld restarted 101210 19:14:19 InnoDB: Started; log sequence number 456 143528628 InnoDB: !!! innodb_force_recovery is set to 4 !!! 101210 19:14:19 [Warning] 'user' entry 'root@PSDB102' ignored in --skip-name-resolve mode. 101210 19:14:19 [Warning] Neither --relay-log nor --relay-log-index were used; so replication may break when this MySQL server acts as a slave and has his hostname changed!! Please use '--relay-log=mysqld-relay-bin' to avoid this problem. 101210 19:14:19 [Note] Event Scheduler: Loaded 0 events 101210 19:14:19 [Note] /usr/sbin/mysqld: ready for connections. Version: '5.1.31-1ubuntu2-log' socket: '/var/run/mysqld/mysqld.sock' port: 3306 (Ubuntu) 101210 19:14:32 InnoDB: error: space object of table mydb/__twitter_friend, InnoDB: space id 1602 did not exist in memory. Retrying an open. 101210 19:14:32 InnoDB: error: space object of table mydb/access_request, InnoDB: space id 1318 did not exist in memory. Retrying an open. 101210 19:14:32 InnoDB: error: space object of table mydb/activity, InnoDB: space id 1595 did not exist in memory. Retrying an open. 101210 19:14:32 - mysqld got signal 11 ; This could be because you hit a bug. It is also possible that this binary or one of the libraries it was linked against is corrupt, improperly built, or misconfigured. This error can also be caused by malfunctioning hardware. We will try our best to scrape up some info that will hopefully help diagnose the problem, but since we have already crashed, something is definitely wrong and this may fail. key_buffer_size=16777216 read_buffer_size=131072 max_used_connections=1 max_threads=600 threads_connected=1 It is possible that mysqld could use up to key_buffer_size + (read_buffer_size + sort_buffer_size)*max_threads = 1328077 K bytes of memory Hope that's ok; if not, decrease some variables in the equation. thd: 0x1753c070 Attempting backtrace. You can use the following information to find out where mysqld died. If you see no messages after this, something went terribly wrong... stack_bottom = 0x7f7a0b5800d0 thread_stack 0x20000 /usr/sbin/mysqld(my_print_stacktrace+0x29) [0x8b4f89] /usr/sbin/mysqld(handle_segfault+0x383) [0x5f8f03] /lib/libpthread.so.0 [0x7f7cbc350080] /usr/sbin/mysqld(ha_innobase::innobase_get_index(unsigned int)+0x46) [0x77c516] /usr/sbin/mysqld(ha_innobase::innobase_initialize_autoinc()+0x40) [0x77c640] /usr/sbin/mysqld(ha_innobase::open(char const*, int, unsigned int)+0x3f3) [0x781f23] /usr/sbin/mysqld(handler::ha_open(st_table*, char const*, int, int)+0x3f) [0x6db00f] /usr/sbin/mysqld(open_table_from_share(THD*, st_table_share*, char const*, unsigned int, unsigned int, unsigned int, st_table*, bool)+0x57a) [0x64760a] /usr/sbin/mysqld [0x63f281] /usr/sbin/mysqld(open_table(THD*, TABLE_LIST*, st_mem_root*, bool*, unsigned int)+0x626) [0x641e16] /usr/sbin/mysqld(open_tables(THD*, TABLE_LIST**, unsigned int*, unsigned int)+0x5db) [0x6429cb] /usr/sbin/mysqld(open_normal_and_derived_tables(THD*, TABLE_LIST*, unsigned int)+0x1e) [0x642b0e] /usr/sbin/mysqld(mysqld_list_fields(THD*, TABLE_LIST*, char const*)+0x22) [0x70b292] /usr/sbin/mysqld(dispatch_command(enum_server_command, THD*, char*, unsigned int)+0x146d) [0x60dc1d] /usr/sbin/mysqld(do_command(THD*)+0xe8) [0x60dda8] /usr/sbin/mysqld(handle_one_connection+0x226) [0x601426] /lib/libpthread.so.0 [0x7f7cbc3483ba] /lib/libc.so.6(clone+0x6d) [0x7f7cbae91fcd] Trying to get some variables. Some pointers may be invalid and cause the dump to abort... thd->query at 0x1754d690 = thd->thread_id=1 thd->killed=NOT_KILLED The manual page at http://dev.mysql.com/doc/mysql/en/crashing.html contains information that should help you find out what is causing the crash.

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• While loop read multiple lines from a grep

  - by Basil

  I'm writing a script in AIX 5.3 that will loop through the output of a df and check each volume against another config file. If the volume appears in the config file, it will set a flag which is needed later in the script. If my config file only has a single column and I use a for loop, this works perfectly. My problem, however, is that if I use a while read loop to populate more than one variable per line, any variables I set between the while and the done are discarded. For example, assuming the contents of /netapp/conf/ExcludeFile.conf are a bunch of lines containing two fields each: volName="myVolume" utilization=70 thresholdFlag=0 grep volName /netapp/conf/ExcludeFile.conf | while read vol threshold; do if [ $utilization -ge $threshold ] ; then thresholdFlag=1 fi done echo "$thresholdFlag" In this example, thresholdFlag will always be 0, even if the volume appears in the file and its utilization is greater than the threshold. I could have added an echo "setting thresholdFlag to 1" in there, see the echo, and it'll still echo a 0 at the end. Is there a clean way to do this? I think my while loop is being done in a subshell, and changes I make to variables in there are actually being made to local variables that are discarded after the done.

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• mysql - moving to a lower performance server, how small can I go?

  - by pedalpete

  I've been running a site for a few years now which really isn't growing in traffic, and I want to save some money on hosting, but keep it going for the loyal users of the site and api. The database has one a nearly 4 million row table, and on a 4gb dual xeon 5320 server. When I check server stats on this server with ps -aux, i get returns of mysql running at about 11% capacity, so no serious load. The main query against mysql runs in about 0.45 seconds. I popped over to linode.com to see what kind of performance I could get out of one of their tiny boxes, and their 360mb ram XEN vps returns the same query in 20 seconds. Clearly not good enough. I've looked at the mysql variables, and they are both very similar (I've included the show variables output below, if anybody is interested). Is there a good way to decide on what size server is needed based on what I'm coming from? Is it RAM that is likely making the difference with the large table size? Is there a way for me to figure out how much ram would be ideal?? Here's the output of the show variables (though I'm not sure it is important). +---------------------------------+------------------------------------------------------------+ | Variable_name | Value | +---------------------------------+------------------------------------------------------------+ | auto_increment_increment | 1 | | auto_increment_offset | 1 | | automatic_sp_privileges | ON | | back_log | 50 | | basedir | /usr/ | | bdb_cache_size | 8384512 | | bdb_home | /var/lib/mysql/ | | bdb_log_buffer_size | 262144 | | bdb_logdir | | | bdb_max_lock | 10000 | | bdb_shared_data | OFF | | bdb_tmpdir | /tmp/ | | binlog_cache_size | 32768 | | bulk_insert_buffer_size | 8388608 | | character_set_client | latin1 | | character_set_connection | latin1 | | character_set_database | latin1 | | character_set_filesystem | binary | | character_set_results | latin1 | | character_set_server | latin1 | | character_set_system | utf8 | | character_sets_dir | /usr/share/mysql/charsets/ | | collation_connection | latin1_swedish_ci | | collation_database | latin1_swedish_ci | | collation_server | latin1_swedish_ci | | completion_type | 0 | | concurrent_insert | 1 | | connect_timeout | 10 | | datadir | /var/lib/mysql/ | | date_format | %Y-%m-%d | | datetime_format | %Y-%m-%d %H:%i:%s | | default_week_format | 0 | | delay_key_write | ON | | delayed_insert_limit | 100 | | delayed_insert_timeout | 300 | | delayed_queue_size | 1000 | | div_precision_increment | 4 | | keep_files_on_create | OFF | | engine_condition_pushdown | OFF | | expire_logs_days | 0 | | flush | OFF | | flush_time | 0 | | ft_boolean_syntax | + - For some reason, that table formats properly in the preview, but apparently not when viewing the question. Hopefully it isn't needed anyway.

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• Puppet: variable overriding best practices

  - by rvs

  I'm wondering what are best practices for overriding variables in puppet. I'd like to have all my nodes (which located in different places, some of them are qa, some live) with same classes. Now I have something like this: class base_linux { <...> # something which requires $env and $relayhost variables } class linux_live { $relayhost="1.1.1.1" $env = "prod" include base_linux } class linux_qa { $relayhost="2.2.2.2" # override relayhost include base_linux } class linux_trunk { $env = "trunk" # override env inlude linux_qa } node "trunk01" { include linux_trunk include <something else> } node "trunk02" { $relayhost = "3.3.3.3" # override relayhost include linux_trunk include <something else> } node "prod01" { include linux_prod } So, I'd like to have some defaults in base_linux, which can be overrided by linux_qa/linux_live, which can be overrided in higher level classes and node definition. Of course, it does not work (and not expected to work). It does not work with class inheritance as well. Probably, I'll be able to archive using global scope variables, but it does not seems like a good idea to me. What is the best way to solve this problem?

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• How do I take input/output from a form and store it in a JS variable?

  - by marcamillion

  I am creating the UI of a web app, and haven't done any back-end work yet. For testing purposes, I want my forms to be able to work, so I want to take the input they have received and store it in javascript variables so I can access them, using jQuery. Everything I have looked at, tells me how to pass js variables into the form, not the other way around. Any ideas? Thanks.

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• I dont understand Access modifiers in OOP (JAVA)

  - by Imran

  I know this is a silly question but i don't understand Access Modifiers in OOP. Why do we make for example in JAVA instance variables private and then use public getter and setter methods to access them? I mean whats the reasoning/logic behind this? You still get to the instance variable but why use setter and getter methods when you can just make your variables public? please excuse my ignorance as i'm simply trying to understand why we do this? Thank you in advance;-)

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• Closest Ruby representation of a 'private static final' and 'public static final' class variable in

  - by Hosh

  Given the Java code below, what's the closest you could represent these two static final variables in a Ruby class? And, is it possible in Ruby to distinguish between private static and public static variables as there is in Java? public class DeviceController { ... private static final Device myPrivateDevice = Device.getDevice("mydevice"); public static final Device myPublicDevice = Device.getDevice("mydevice"); ... public static void main(String args[]) { ... } }

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• Dealloc on my custom objective-C

  - by VansFannel

  Hello. I'm developing an iPhone application, and I very new on iPhone development. I've created some custom classes with instance variables (NSArray, NSString, etc.). All classes inherits from NSObject. Should I create a dealloc method to release all instance variables? Thank you.

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• Swapping two variable value without using 3rd variable

  - by Muhammad Akhtar

  One of the very tricky question asked in an interview... we need to swap the values of two variables like a=10 and b=15 Generaly to swap two variables values, we need 3rd variable like.. temp=a a=b b=temp Now the requirement is, swaping value of two variable values without using 3rd variable? How can be accopmplish this?

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• JavaScript Variable Scope

  - by lYriCAlsSH

  What is the scope of variables in javascript? Do they have the same scope inside as opposed to outside a function? Or does it even matter? Also, where are the variables stored if they are defined globally?

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• How can this C and PHP programmer learn Ruby and Rails?

  - by Winston

  I came from a C, php and bash background, it was easy to learn because they all have the same C structure, which I can associate with what I already know. Then 2 years ago I learned Python and I learned it quite well, Python is easier for me to learn than Ruby. Then since last year, I was trying to learn Ruby, then Rails, and I admit, until now I still couldn't get it, the irony is that those are branded as easy to learn, but for a seasoned programmer like me, I just couldn't associate it with what I learned before, I have 2 books on both Ruby and Rails, and when I'm reading it nothing is absorbed into my mind, and I'm close to giving up... In ruby, I'm having a hard time grasping the concepts of blocks, and why there's @variables that can be accessed by other functions, and what does $variable and :variable do? And in Rails, why there's function like this_is_another_function_that_do_this, so thus ruby, is it just a naming convention or it's auto-generated with thisvariable _can_do_this_function. I'm still puzzled that where all those magic concepts and things came from? And now, 1 year of trying and absorbing, but still no progress... Edit: To summarize: How can I learn about blocks, and how can it be related to concepts from PHP/C? Variables, what does does it mean when a variable is prefixed with: @ $ : "Magic concepts", suchs as rails declarations of Records, what happens behind the scenes when I write has_one X OK so, bear with me with my confusion, at least I'm honest with myself, and it's over a year now since I first trying to learn ruby, and I'm not getting younger.. so I learned this in Bash/C/PHP solve_problem($problem) { if [ -e $problem == "trivial" ]; then write_solution(); else breakdown_problem_into_N_subproblems(\; define_relationship_between_subproblems; for i in $( command $each_subproblem ); do solve_problem $i done fi } write_solution(problem) { some_solution=$(command <parameters> "input" | command); command | command $some_solution > output_solved_problem_to_file } breakdown_problem_into_N_subproblems($problems) { for i in $problems; do command $i | command > i_can_output_a_file_right_away done } define_relationship_between_subproblems($problems) { if [ -e $problem == "relationship" ]; then relationship=$(command; command | command; command;) elsif [ -e $problem == "another_relationship" ]; relationship=$(command; command | command; command;) fi } In C/PHP is something like this solve_problem(problem) { if (problem == trivial) write_solution; else { breakdown_problem_into_N_subproblems; define_relationship_between_subproblems; for (each_subproblem) solve_problems(subproblem); } } And now, I just couldn't connect the dots with Ruby, |b|{ blocks }, using @variables, :variables, and variables_with_this_things..

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• How to pass the 'argument-line' of one PowerShell function to another?

  - by jwfearn

  I'm trying to write some PowerShell functions that do some stuff and then transparently call through to existing built-in function. I want to pass along all the arguments untouched. I don't want to have to know any details of the arguments. I tired using 'splat' to do this with @args but that didn't work as I expected. In the example below, I've written a toy function called myls which supposed to print hello! and then call the same built-in function, Get-ChildItem, that the built-in alias ls calls with the rest of the argument line intact. What I have so far works pretty well: function myls { Write-Output "hello!" Invoke-Expression("Get-ChildItem "+$MyInvocation.UnboundArguments -join " ") } A correct version of myls should be able to handle being called with no arguments, with one argument, with named arguments, from a line containing multiple semi-colon delimited commands, and with variables in the arguments including string variables containing spaces. The tests below compare myls and the builtin ls: [NOTE: output elided and/or compacted to save space] PS> md C:\p\d\x, C:\p\d\y, C:\p\d\"jay z" PS> cd C:\p\d PS> ls # no args PS> myls # pass PS> cd .. PS> ls d # one arg PS> myls d # pass PS> $a="A"; $z="Z"; $y="y"; $jz="jay z" PS> $a; ls d; $z # multiple statements PS> $a; myls d; $z # pass PS> $a; ls d -Exclude x; $z # named args PS> $a; myls d -Exclude x; $z # pass PS> $a; ls d -Exclude $y; $z # variables in arg-line PS> $a; myls d -Exclude $y; $z # pass PS> $a; ls d -Exclude $jz; $z # variables containing spaces in arg-line PS> $a; myls d -Exclude $jz; $z # FAIL! Is there a way I can re-write myls to get the behavior I want?

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• Big datastructures in functional programming

  - by Denis Gorodetskiy

  I'm newbie in Functional Programming. I have a huge neural network with thousands of neurons and every connection between neurons has its weight. I have to update these weights very often, several thousand times per learning session. Is FP still applicable here? I mean in fp we can't modify variables and only able to return new variables not changing previous values. Does this mean I have to recreate whole network on every weight update?

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• Is there a compiled* programming language with dynamic, maybe even weak typing?

  - by sub

  I wondered if there is a programming language which compiles to machine code/binary (not bytecode then executed by a VM, that's something completely different when considering typing) that features dynamic and/or weak typing, e.g: Think of a compiled language where: Variables don't need to be declared Variables can be created doing runtime Functions can return values of different types Questions: Is there such a programming language? (Why) not? I think that a dynamically yet strong typed, compiled language would really sense, but is it possible?

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• Create a Session in Django

  - by Reznor

  So far the Documentation for Django has been too technical. How do I create a session and store variables in it or get variables from it? I'm new to the Django framework, hence why the Documentation is too technical. Sessions are my 'last step'.

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• Hibernate - on the stack or on the heap?

  - by Stephano

  As a Java programmer, you usually keep two truths in your pocket: Instance variables and Objects lie on Heap. Local variables and methods lie on the Stack. Now that I use Hibernate in just about everything, I realize I'm not as sure of myself. Are there some good rules of thumb for using hibernate and knowing where your memory lives?

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• Is there a ColdFusion equivalent to PHP for include_once?

  - by davidosomething

  I've been adding this to my pages: pagewithinclude.cfm <cfinclude template = "_pagename.cfm"> _pagename.cfm <cfif Not IsDefined("variables.included_pagename")> <cfparam name = "variables.included_pagename" default = "1"> rest of page </cfif> Is there a better way in CF? Something similar to PHP's include_once?

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• Debugging mod_rewrite

  - by nickf

  I'm playing around with Apache's mod_rewrite module, and want to know if there is a decent way to output some debugging information? For example, the documentation lists a number of variables available: %{HTTP_USER_AGENT}, %{HTTP_REFERER}, %{HTTP_COOKIE} ... etc Is there a way I could output these just to see what I'm working with? I set up the RewriteLog (Level 2) and have been looking at that, but it'd be nice to be able to see the value of the variables.

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• Populating PHP list() with values in an array.

  - by Mike

  Hi, I have an array: $arr = array('foo', 'bar', 'bash', 'monkey', 'badger'); I want to have the elements in that array appear as the variables in my list(): list($foo, $bar, $bash, $monkey, $badger) = $data; Without actually specifying the variables, I tried; list(implode(",$", $arr)) = $data; and list(extract($arr)) = $data; But they don't work, I get: Fatal error: Can't use function return value in write context Does anyone have any idea whether this is possible? Cheers, Mike

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• In Clojure, how to define a variable named by a string?

  - by Carl Smotricz

  Given a list of names for variables, I want to set those variables to an expression. I tried this: (doall (for [x ["a" "b" "c"]] (def (symbol x) 666))) ...but this yields the error java.lang.Exception: First argument to def must be a Symbol Can anyone show me the right way to accomplish this, please?

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• how to insert new line in bash shell for variable??

  - by puspa

  I have two variables var1 and var2. The contents of each variables come from bash shell grep command. echo $var1 prints 123 465 326 8080 echo $var2 prints sila kiran hinal juku Now I want to print the above into following formats in Linux bash shell 123 sila 465 kiran 326 hinal 8080 juku So how can I print this way in bash shell??

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• Passing a DefaultHttpClient between activites

  - by searchMaker

  Hi all, I am trying to maintain my session variables that I get back in a cookie from my website in my DefaultHttpClient by passing the client between activities. Simply put how can I pass this object between activities to maintain my session variables? Bundle.put... doesn't seem to support this object. If it does how does it work with DefaultHttpClient? Thanks in advance to anyone who can help.

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• Access modifiers in Object-Oriented Programming

  - by Imran

  I don't understand Access Modifiers in OOP. Why do we make for example in Java instance variables private and then use public getter and setter methods to access them? I mean what's the reasoning/logic behind this? You still get to the instance variable but why use setter and getter methods when you can just make your variables public? please excuse my ignorance as I am simply trying to understand why? Thank you in advance. ;-)

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• assign operator to variable in python?

  - by abhilashm86

  Usual method of applying mathematics to variables is a * b Is it able to calculate and manipulate two operands like this? a = input('enter a value') b = input('enter a value') op = raw_input('enter a operand') then how do i connect op and two variables a and b?? i know i can compare op to +, -, %, $ and then assign and compute.... but can i do something like a op b , how to tell compiler that op is an operator?? any tweaks possible?

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• c declaraing varibles in blocks

  - by anon

  I know that in C++, I can declare variables pretty much everywhere. I recall once reading that in C, variables must be declared at the top of a function i.e. the following is invalid: void foo() { int good; if (...) { int bad; } } In the above code, is the declaraing of the bad varaible legal by C standards, or only legal due to a gcc extension? Thanks!

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