Ceroce

-module(recursion).
-export([fib/1, fibtail/1, fibtail/3, isPerfect/1]).

fib(0) ->
    0;
fib(1) ->
    1;
fib(N) when N > 0 ->
    fib(N-1)+fib(N-2).

palkan

Installation

Go to the official website and choose your OS.

MacOS

Docker for Mac has a problem is the disk IO performance (see docker/for-mac#77).

There is a fix (https://github.com/IFSight/d4m-nfs) which makes Docker use NFS instead of OSXFS.

palkan

-- show running queries (9.2)
SELECT pid, age(query_start, clock_timestamp()), usename, query 
FROM pg_stat_activity 
WHERE query != '<IDLE>' AND query NOT ILIKE '%pg_stat_activity%' 
ORDER BY query_start desc;

-- kill running query
SELECT pg_cancel_backend(procpid);

-- kill idle query

steinwaywhw

• Use curl to get the JSON response for the latest release
• Use grep to find the line containing file URL
• Use cut and tr to extract the URL
• Use wget to download it

curl -s https://api.github.com/repos/jgm/pandoc/releases/latest \
| grep "browser_download_url.*deb" \
| cut -d : -f 2,3 \
| tr -d \" \

lfender6445

Pry Cheat Sheet

• Youtube Tutorial 2013

Command Line

• pry -r ./config/app_init_file.rb - load your app into a pry session (look at the file loaded by config.ru)
• pry -r ./config/environment.rb - load your rails into a pry session

Debugger

zhengjia

=Navigating=
    visit('/projects')
    visit(post_comments_path(post))

=Clicking links and buttons=
    click_link('id-of-link')
    click_link('Link Text')
    click_button('Save')
    click('Link Text') # Click either a link or a button
    click('Button Value')