Google's Go Programming Language - Introduction

Google’s Go
Introduction to the next “C” language!
S G Ganesh

Agenda
 Introduction to Go (What is “Go”?)
 “Hello world” in Go
 Examples for “getting a hang of” Go
 Examples using some novel features
 Implementation status
 Resources
 Let’s Go!

First things first: Setting the stage
 It’s not possible to cover all details of a new language in a
45-mins presentation
 We’ll quickly cover most important aspects of Go
 Can’t drink ocean in a day – let alone in an hour!
 No one is an “expert” in Go yet
 Creators of the language are the only experts right now
 I am an early adopter and got hooked-on to the
language
 I am making this presentation based on my experience
 For many questions, there are no right or wrong answers:
 Go is still an evolving language and answers might
change!

So, what’s all the buzz about?
 Go: new programming language announced by Google (Sep 09)
 Created lots of excitement in the programming community
 Many tout it as the next C language
 ‘C’ evolved from ‘B’; many languages are named as ‘D’, or
want to be the ‘D’ language
 But nothing has made the cut so far; “Go” might (or will it be
“Gone” in a few years ;-) )
 Is there substance behind hype?
 Yes, a lot! Most system programmers find it very good
 Go won Tiobe’s ‘language of the year award 2009’
 Tiobe is a programming language popularity index:
http://www.tiobe.com/
 Latest status (march 2010)

Okay, so what’s Go?
 Go is a new, experimental, concurrent, garbage-collected,
systems-programming language.
 New & Experimental: Go is still at experimental stage
 with tools, packages etc. still in development.
 No production system implemented using Go till now
 Concurrent: Supports 'communication channels’ for
concurrency - Communicating Sequential Processes (CSP).
 Garbage-collected: The memory is automatically garbage
collected
 For systems-programming: Intended for writing things like
compilers, web servers…

Still, we can use it as a general purpose language.

Who’s behind Go?
 Robert Griesemer, Ken Thompson (of Unix
fame), and Rob Pike are the creators of the
language.
 All three are well-known in programming community
 This is how things fell in place:
 Go project was started around May 2007. Ken Thompson
wrote a Go compiler and runtime from scratch.
 By mid of 2008, working compiler and runtime was ready.
 Ian Lance Taylor and Russ Cox joined Go team in 2008. Ian
Taylor implemented GCC front-end for Go.

Why a new language?
 This description is as given by the creators
 No major sys. programming language came-up in last
decade. But much has changed during the last decade(s)
 Libraries becoming bigger with lots of dependencies
 Internet and networking is becoming pervasive
 Client/server systems, massive clusters used today
 Multi-core processors becoming mainstream.
 Systems programming languages were not designed with
these in mind.
 Other reasons
 construction (enterprise software) has become very slow
 OOP using inheritance hierarchies not effective

Goals of the language
 Efficiency and ease of use:
 Efficiency of C, but ease like Ruby.
 Performance: within 10%-20% of equivalent C
 Safe to use:
 Both type-safe as well as memory-safe.
 Concurrency:
 Good support for concurrency and communication
 Garbage Collected:
 "Attempts" to build an efficient, and latency-free Garbage
Collection mechanism.
 High-speed builds:
 Fast compilation & linking

Some important capabilities of Go
 Simplicity: GO has a clean and concise syntax
 Characteristic of Google products
 For example, light-weight type system
 Use it to believe it
 Separation of interface and the implementation
 I know it’s often misused statement, but Go has it!
 Arguably a novel feature of Go
 Goroutines
 Is based on CSP: much safer than lock-based, like Java
 And more:
 E.g. Reflection (yes! but this is systems prog. lang!)

Enough theory, lets see examples!
 All programs in Go should be in a package, its “main”
here
 We import “fmt” package for using Printf function
 Execution starts with ‘main.main()’ function
 Functions have “func” keyword
 Printf is in fmt package

Now we’ll find factorial of a number
 Lack of declarations
 “fact” and “i” inferred as “ints” from init value 1 because of :=
 “for” loop is the only loop construct supported in Go
 Others like “while” are variations of “for”
 An example of minimal features
 Note the lack of semi-colons
 Have to use only if “necessary”

Looks like C, but not C!
 Go has elegant declaration syntax
 See how arguments are passed and returned
 Not like C: it is infamous for its declaration syntax
 Can return multiple values from functions
 See swap for similar functionality in = operator
 Example for “orthogonal” language features

Built-in support for features like maps
 Maps are built-in, so no need to import
 Initialized with pair separated by “:”
 “range” keyword is useful for traversal
 Using a for loop
 Works for slices, strings etc. (“orthogonal” feature)

Functions as first class objects
 Functions are first
class objects in Go
 We can have
“function literals”
(similar to
“closures” in
functional
languages) for
example

Structures
 Structs are declared with type keyword
 We can have struct literals
 Created in heap
 And print struct members using %v in Printf

Methods
 Methods are implemented by specifying the struct
name before the method name

Interfaces: A novel feature
 Interfaces specified with
‘interface’ keyword
 Not same as in C#/Java
 The structs doesn’t have to
say it implements an
interface
 Any struct that implements
the methods as specified
by any interface satisfies
that interface
 Strict static type checking &
“duck typing”!

Goroutines: easy & safe multithreading
 Goroutines are functions executing in parallel
 in the same address space in stack
 They communicate using “channels” (based on CSP)
 Cleaner, simpler and less-bug prone than using locks
 This shows an example* of how a Sort on big list can be done in
parallel with some other computation

We haven’t covered a lot!
 Important features not covered because of limited time
 reflection, embedding structs (aka inheritance), package
construction etc.
 Lots of libraries already implemented
 math, crypto, networking, regex, OS, testing, html gen….
 Garbage collection & Go runtime capabilities
 Currently mark-and-sweep collector, but better ones under
construction
 Small runtime: GC, channels, stack allocation, goroutines
etc.

Implementation status
 Currently compiler tool-chain available for Mac & Linux
 No “official” windows port; “unofficial” old ports exist
 Compilers: GCC implementation and a stand-alone implementation
 You can download the compilers/tools from this website & try it
 It’s open source (BSD license): We can contribute!
 Lots of work going on in libraries and improving the existing
tool chain
 Frequent builds & releases, quick response times etc.
 Many features & tools still lacking in Go
 For example, generics and debugger tool

Resources
 Go websites:
 Official: www.golang.org (web server implemented in Go!)
 Unofficial: http://go-lang.cat-v.org/
 Want to learn Go?
 No “books” yet
 Read "Effective Go” (http://golang.org/doc/effective_go.html)
 tutorials available online
 Tech talk (http://www.youtube.com/watch?v=rKnDgT73v8s)
 Join go-nuts mailing list gonuts@googlegroups.com
 You can try (compile & run) Go programs online!
 This is really useful: http://ideone.com/

So what are you waiting for?
 Lets Go!

Google's Go Programming Language - Introduction

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