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| <title>Go (January 12, 2010)</title> |
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| <br/> |
| <br/> |
| <h1 style="padding-right: 0pt; margin-right: 0pt; color: #0066cc; font-size: 250%; border-bottom: 0px;">The Go Programming Language</h1> |
| <div style="color: #ffcc00;"> |
| <h2>Russ Cox</h2> |
| <!-- <h3><i>rsc@google.com</i></h3> --> |
| <br/> |
| <h3>Stanford University<br/><br/>January 12, 2010</h3> |
| </div> |
| </div> |
| |
| <div class="slide"> |
| <h1>Go</h1> |
| |
| <h2>New</h2> |
| <h2>Experimental</h2> |
| <h2>Concurrent</h2> |
| <h2>Garbage-collected</h2> |
| <h2>Systems</h2> |
| <h2>Language</h2> |
| </div> |
| |
| <div class="slide"> |
| <h1>Hello, world</h1> |
| <pre> |
| package main |
| |
| import "fmt" |
| |
| func main() { |
| fmt.Printf("Hello, 世界\n") |
| } |
| </pre> |
| </div> |
| |
| <div class="slide"> |
| <h1>History</h1> |
| |
| <h2>Design started in late 2007.</h2> |
| <h2>Implementation starting to work mid-2008.</h2> |
| <h2>Released as an open source project in November 2009.</h2> |
| <h2>Work continues.</h2> |
| <h2>Robert Griesemer, Ken Thompson, Rob Pike, Ian Lance Taylor, Russ Cox, many others</h2> |
| </div> |
| |
| <div class="slide"> |
| <h1>Why?</h1> |
| |
| <h2>Go fast!</h2> |
| <h2>Make programming fun again.</h2> |
| </div> |
| |
| <div class="slide"> |
| <h1>Why isn't programming fun?</h1> |
| |
| <div class="incremental"> |
| <h2>Compiled, statically-typed languages (C, C++, Java) require too much typing and too much typing:</h2> |
| |
| <ul> |
| <li>verbose, lots of repetition</li> |
| <li>too much focus on type hierarchy</li> |
| <li>types get in the way as much as they help</li> |
| <li>compiles take far too long</li> |
| </ul> |
| </div> |
| |
| <div class="incremental"> |
| <h2>Dynamic languages (Python, JavaScript) fix these problems (no more types, no more compiler) but introduce others:</h2> |
| |
| <ul> |
| <li>errors at run time that should be caught statically</li> |
| <li>no compilation means slow code</li> |
| </ul> |
| </div> |
| |
| <h2 class="incremental">Can we combine the best of both?</h2> |
| </div> |
| |
| <div class="slide"> |
| <h1>Go</h1> |
| |
| <h2>Make the language fast.</h2> |
| <h2>Make the tools fast.</h2> |
| </div> |
| |
| <div class="slide"> |
| <h1>Go Approach: Static Types</h1> |
| |
| <h2>Static types, but declarations can infer type from expression:</h2> |
| |
| <pre> |
| var one, hi = 1, "hello" |
| |
| var double = func(x int) int { return x*2 } |
| </pre> |
| |
| <h2>Not full Hindley-Milner type inference.</h2> |
| </div> |
| |
| |
| <div class="slide"> |
| <h1>Go Approach: Methods</h1> |
| |
| <h2>Methods can be defined on any type.</h2> |
| |
| <pre> |
| type Point struct { |
| X, Y float64 |
| } |
| |
| func (p Point) Abs() float64 { |
| return math.Sqrt(p.X*p.X + p.Y*p.Y) |
| } |
| </pre> |
| </div> |
| |
| <div class="slide"> |
| <h1>Go Approach: Methods</h1> |
| |
| <h2>Methods can be defined on any type.</h2> |
| |
| <pre> |
| type MyFloat float64 |
| |
| func (f MyFloat) Abs() float64 { |
| v := float64(f) |
| if v < 0 { |
| v = -v |
| } |
| return v |
| } |
| </pre> |
| </div> |
| |
| <div class="slide"> |
| <h1>Go Approach: Abstract Types</h1> |
| |
| <h2>An interface type lists a set of methods. Any value with those methods satisfies the interface.</h2> |
| |
| <pre> |
| type Abser interface { |
| Abs() float64 |
| } |
| |
| func AbsPrinter(a Abser) |
| </pre> |
| |
| <h2>Can use Point or MyFloat (or ...):</h2> |
| |
| <pre> |
| p := Point{3, 4} |
| AbsPrinter(p) |
| |
| f := MyFloat(-10) |
| AbsPrinter(f) |
| </pre> |
| |
| <h2>Notice that Point never declared that it implements Abser. It just does. Same with MyFloat.</h2> |
| </div> |
| |
| <div class="slide"> |
| <h1>Go Approach: Packages</h1> |
| |
| <h2>A Go program comprises one or more packages.</h2> |
| <h2>Each package is one or more source files compiled and imported as a unit.</h2> |
| <pre> |
| package draw |
| |
| type Point struct { |
| X, Y int |
| } |
| </pre> |
| |
| <pre> |
| package main |
| |
| import "draw" |
| |
| var p draw.Point |
| </pre> |
| </div> |
| |
| <div class="slide"> |
| <h1>Go Approach: Visibility</h1> |
| |
| <h2>Inside a package, all locally defined names are visible in all source files.</h2> |
| |
| <h2>When imported, only the upper case names are visible.</h2> |
| |
| <pre> |
| package draw |
| |
| type <span style="color: black;">Point</span> struct { |
| <span style="color: black;">X</span>, <span style="color: black;">Y</span> int |
| dist float64 |
| } |
| |
| type cache map[Point] float64 |
| </pre> |
| |
| <h2>Clients that <code>import "draw"</code> can use the black names only.</h2> |
| |
| <h2>“Shift is the new <code>public</code>.”</h2> |
| </div> |
| |
| <div class="slide"> |
| <h1>Go Approach: Concurrency</h1> |
| |
| <h2>Cheap to create a new flow of control (goroutine):</h2> |
| |
| <pre> |
| func main() { |
| go expensiveComputation(x, y, z) |
| anotherExpensiveComputation(a, b, c) |
| } |
| </pre> |
| |
| <h2>Two expensive computations in parallel.</h2> |
| </div> |
| |
| <div class="slide"> |
| <h1>Go Approach: Synchronization</h1> |
| |
| <h2>Use explicit messages to communicate and synchronize.</h2> |
| |
| <pre> |
| func computeAndSend(ch chan int, x, y, z int) { |
| ch <- expensiveComputation(x, y, z) |
| } |
| |
| func main() { |
| ch := make(chan int) |
| go computeAndSend(ch, x, y, z) |
| v2 := anotherExpensiveComputation(a, b, c) |
| v1 := <-ch |
| fmt.Println(v1, v2) |
| } |
| </pre> |
| <h2>Notice communication of result in addition to synchronization.</h2> |
| </div> |
| |
| <div class="slide"> |
| <h1>Go Fast: Language</h1> |
| |
| <h2 class="incremental">Static types: enough to compile well, but inferred much of the time.</h2> |
| |
| <h2 class="incremental">Methods: on any type, orthogonal to type system.</h2> |
| |
| <h2 class="incremental">Abstract types: interface values, relations inferred statically.</h2> |
| |
| <h2 class="incremental">Visibility: inferred from case of name.</h2> |
| |
| <h2 class="incremental">Concurrency: lightweight way to start new thread of control.</h2> |
| |
| <h2 class="incremental">Synchronization: explicit, easy message passing.</h2> |
| |
| <br/> |
| |
| <h2 class="incremental">Lightweight feel of a scripting language but compiled.</h2> |
| </div> |
| |
| <div class="slide"> |
| <h1>Compile fast</h1> |
| |
| <div class="incremental"> |
| <h2>Observation: much of the compile time for a source file is spent processing |
| other, often unrelated files.</h2> |
| |
| <h2>In C: <code>a.c</code> includes <code>b.h</code>, which includes <code>c.h</code>, which includes <code>d.h</code>. |
| </h2> |
| |
| <h2>Except that it's more often a tree instead of a chain.</h2> |
| |
| <h2>On my Mac (OS X 10.5.8, gcc 4.0.1):</h2> |
| <ul> |
| <li>C: <code>#include <stdio.h></code> reads 360 lines from 9 files.</li> |
| <li>C++: <code>#include <iostream></code> reads 25,326 lines from 131 files.</li> |
| <li>Objective C: <code>#include <Carbon/Carbon.h></code> reads 124,730 lines from 689 files.</li> |
| </ul> |
| |
| <h2>And we haven't done any real work yet!</h2> |
| |
| <h2>Same story in Java, Python, but reading binaries instead of source files.</h2> |
| </div> |
| </div> |
| |
| <div class="slide"> |
| <h1>Implementation: Summarize Dependencies</h1> |
| |
| <pre> |
| package gui |
| |
| import "draw" |
| |
| type Mouse struct { |
| Loc draw.Point |
| Buttons uint |
| } |
| </pre> |
| <h2>Compiled form of <code>gui</code> summarizes the necessary part of <code>draw</code> (just <code>Point</code>).</h2> |
| |
| </div> |
| |
| <div class="slide"> |
| <h1>Implementation: Summarize Dependencies</h1> |
| |
| <h2>Compiled form of <code>gui</code> summarizes the necessary part of <code>draw</code> (just <code>Point</code>). Pseudo-object:</h2> |
| |
| <pre> |
| package gui |
| type draw.Point struct { |
| X, Y int |
| } |
| type gui.Mouse struct { |
| Loc draw.Point |
| Buttons uint |
| } |
| </pre> |
| |
| <h2>A file that imports <code>gui</code> compiles without consulting <code>draw</code> or its dependencies.</h2> |
| |
| <h2>In Go: <code>import "fmt"</code> reads <i>one</i> file: 184 lines summarizing types from 7 packages.</h2> |
| |
| <h2>Tiny effect in this program but can be exponential in large programs.</h2> |
| </div> |
| |
| <div class="slide"> |
| <h1>Compilation Demo</h1> |
| |
| <h2>Build all standard Go packages: ~120,000 lines of code.</h2> |
| </div> |
| |
| <div class="slide"> |
| <h1>Go Status</h1> |
| |
| <div class="incremental"> |
| <div> |
| <h2>Open source:</h2> |
| <ul> |
| <li>released on November 10, 2009</li> |
| <li>regular releases (~ weekly)</li> |
| <li>all development done in public Mercurial repository</li> |
| <li>outside contributions welcome</li> |
| </ul> |
| </div> |
| |
| <div> |
| <h2>Portable:</h2> |
| <ul> |
| <li>FreeBSD, Linux, OS X (x86, x86-64)</li> |
| <li>(in progress) Linux arm, Native Client x86, Windows x86.</li> |
| </ul> |
| </div> |
| |
| <div> |
| <h2>Still in progress, experimental. Yet to come:</h2> |
| <ul> |
| <li>mature garbage collector</li> |
| <li>generics?</li> |
| <li>exceptions?</li> |
| <li>unions or sum types?</li> |
| </ul> |
| </div> |
| </div> |
| |
| </div> |
| |
| <div class="slide titlepage"> |
| <h1>Questions?</h1> |
| <br><br> |
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| </center> |
| <br><br> |
| <div style="color: #ffcc00;"> |
| <!-- <h3><i>rsc@google.com</i></h3> --> |
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