book

Introducing Erlang

by Simon St. Laurent

January 2013

Beginner to intermediate

204 pages

4h 26m

English

O'Reilly Media, Inc.

Read now

Unlock full access

Who This Book Is ForWho This Book Is Not ForWhat This Book Will Do For YouHow This Book WorksWhy I Wrote This BookOther ResourcesEtudes for ErlangAre You Sure You Want Erlang?Erlang Will Change YouConventions Used in This BookA Note on Erlang SyntaxUsing Code ExamplesHelp This Book GrowPlease Use It For GoodSafari® Books OnlineHow to Contact UsContent UpdatesApril 2, 2013Acknowledgments
InstallationFiring It UpFirst Steps: The ShellMoving through TextMoving through HistoryMoving through FilesDoing SomethingCalling FunctionsNumbers in ErlangWorking with Variables in the ShellSeeing Your Bound VariablesClearing Bound Variables in the Shell
Fun with funDefining ModulesFrom Module to FunFunctions and Variable ScopeModule DirectivesDocumenting CodeDocumenting ModulesDocumenting FunctionsDocumenting Your Application
AtomsPattern Matching with AtomsAtomic BooleansGuardsUnderscoring That You Don’t CareAdding Structure: TuplesPattern Matching with TuplesProcessing Tuples
Logic Inside of FunctionsEvaluating CasesIf This, Then ThatVariable Assignment in case and if ConstructsThe Gentlest Side Effect: io:formatSimple RecursionCounting DownCounting UpRecursing with Return Values
StringsAsking Users for InformationGathering TermsGathering CharactersReading Lines of Text
List BasicsSplitting Lists into Heads and TailsProcessing List ContentCreating Lists with Heads and TailsMixing Lists and TuplesBuilding a List of Lists
Simple Higher-Order FunctionsCreating New Lists with Higher-Order FunctionsReporting on a ListRunning List Values Through a FunctionFiltering List ValuesBeyond List ComprehensionsTesting ListsSplitting ListsFolding Lists
The Shell Is a ProcessSpawning Processes from ModulesLightweight ProcessesRegistering a ProcessWhen Processes BreakProcesses Talking Amongst ThemselvesWatching Your ProcessesBreaking Things and Linking Processes

Flavors of ErrorsCatching Runtime Errors as They HappenRaising Exceptions with throwLogging Progress and FailureDebugging through a GUITracing MessagesWatching Function Calls
From Tuples to RecordsSetting Up RecordsCreating and Reading RecordsUsing Records in Functions and ModulesStoring Records in Erlang Term StorageCreating and Populating a TableSimple QueriesA Key Feature: Overwriting ValuesETS Tables and ProcessesNext StepsStoring Records in MnesiaStarting up MnesiaCreating TablesReading DataQuery List Comprehensions
Creating Services with gen_serverA Simple SupervisorPackaging an Application
Moving Beyond the ShellDistributed ComputingProcessing Binary DataInput and OutputTesting, Analyzing, and RefactoringNetworking and the WebData StorageExtending ErlangLanguages Built on ErlangCommunitySharing the Gospel of Erlang
Shell CommandsReserved WordsOperatorsGuard ComponentsCommon FunctionsStrings and FormattingData Types for Documentation and Analysis

Content preview from Introducing Erlang

Chapter 10. Storing Structured Data

Tuples and lists are powerful tools for creating complex data structures, but there are two key pieces missing from the story so far. First, tuples are relatively anonymous structures. Relying on a specific order and number of components in tuples can create major maintenance headaches. Second, despite Erlang’s general preference for avoiding side effects, storing and sharing data is a fundamental side effect needed for a wide variety of projects.

Records will help you create labeled sets of information. Erlang Term Storage (ETS) will help you store and manipulate those sets, and the Mnesia database provides additional features for reliable distributed storage.

From Tuples to Records

Tuples let you build complex data structures, but force you to rely on keeping the order and number of items consistent. If you change the sequence of items in a tuple, or if you want to add an item, you have to check through all of your code to make sure that the change propagates smoothly. As your projects grow, and especially if you need to share data structures with code you don’t control, you’ll need a safer way to store and address information.

Records let you create data structures that use names to connect with data rather than order. You can read, write, and pattern match data in a record without having to worry about the details of where in a tuple a field lurks or whether someone’s added a new field.