### Library of mathematical functions (lua)

• math.abs          — take the absolute value        like: math.abs(-5)  = 5
• math.ceil          — up          like: math.ceil(4.3) = 5
• math.floor        — down         like: math.floor(5.8) = 5
• math.random         — take a random number         like: math.random(100)
• math.randomseed        — set random seeds          like: math.randomseed(os.time())
• math.max         — get max number          like: math.max(3.5,5,-8,35) = 35
• math.min          — get min number          like: math.min(3.5,5,-8,35) = -8
• math.sqrt          —  √x       like: math.sqrt(4) = 2
• math.pow          — X^y          like: math.pow(3,4) = 81
• math.modf()       — Divide integers and decimals        like:math.modf(15.98)     15    0.98

• math.pi        —          like: math.pi = 3.14159265358979323846
• math.deg       —  get angle （获取角度）                      like: math.deg(math.pi) = 180
• math.sin         — get sin value              like: math.sin(math.rad(30)) = 0.5
• math.cos       — get cos value           like: math.cos(0.5) = 0.87758256
• math.tan        — get tan value            like: math.tan(0.5) = 0.5463024

### Basic use of SVN (1.3.9)

Online documentation(Chinese, simplified)

The command for Mac OS：

• svn help (?, h)         // you can enter “svn help” or “svn ?” or “svn h” in terminal to get some help
• svn add . –no-ignore –force     // Add all the files in the current directory
• svn update(up)
• svn checkout(co) path
• svn commit -m “message note” ./         //commit files in the current directory
• svn cleanup
• svn status        //view file status  in the current directory

### How to use the Terminal in macOS ？

• cd ~     // navigate to your Home folder
• cd ../     //navigate to the previous folder
• cd    path       // you can drag the Documents folder onto the Terminal window.
• ls           //is the command for listing files
• pwd     //view current path
• mkdir foldername    //create a folder under the current path     like:mkdir test
• touch filename      //create a file        like:touch readme.txt
• open path
• clear         // clear all content on the current window
• du -sh *       //view the folder size

### The use of mysql

The use of mysql ( mysql version:5.6.34 )

•      //create database     like:create database test;
• show databases;     //view all databases
• use databasename;     //change to current database     like:use test;
• drop database databasename;     //delete database     like:drop database test;
• show tables;     //view all tables in the current database
• create table tablename (columnname datatype );      //create table    like:create table test（
id int unsigned not null auto_increment primary key,
name char(8) not null,
sex char(4) not null,
age tinyint unsigned not null,
tel char(13) null default “-“);
• drop table tablename ;      //delete table       like:drop table test;
• alter table oldtablename rename newtablename ;    // rename table    like: alter table test rename test1;
• desc tablename;        //view table info       like:desc test;
• show full fields from tablename;    //show table detail
• truncate table tablename;     //clear all data in the table    like:truncate table test;
• select * from tablename where …;    //query all data in the table    like:select * from users where userId = ‘1’;
• insert into tablename (columnname) values (‘value’) where … ;  //insert      like:insert into users (username,password) values (‘Jerry’,’12345678′) where userId =’1′;
• update tablename set columnname = ‘value’ where … ;     //update     like:update users set username = ‘Jack’ where userId = ‘1’;
• delete from tablename where … ;       //delete     like:delete from users where userId = ‘1’;

• select version();     //view mysql version(In the login state)
• show character set;         //show all character set for mysql
• exit;      //exit mysql