Information-rich programming in F# (ML Workshop 2012)

Information-rich programming in F# (ML Workshop 2012)

• 1.
  Information-rich programming in F# Tomas Petricek, University of Cambridge Don Syme and the F# team, Microsoft ML Workshop (Copenhagen, 13 September, 2012)
• 2.
  The confusion oflanguages
• 3.
  The confusion oflanguages
• 4.
  What is atype provider?
• 5.
  DEMO: Accessing WorldBank Comparing university enrollment rate in Czech Republic and OECD countries
• 6.
  Problems with dataaccess Data is not types with members Use dynamic languages? Need to know names of properties Use code generation and static languages? Enormous scale of data sources Types need to be generated “on demand”
• 7.
  Components of atype provider Type provider IDE Compiler IntelliSense for Type-Check Compile using Provided Types Provided Types Type Provider
• 8.
  Research problems Mapping datasources to types What is a type? What is a value? Types are provided on demand Cannot generate all indicator types at once! Representing data source properties as types Physical units, provenance, temporal properties Adapting to schema change Type soundness is relative w.r.t. data source changes
• 9.
  Mapping data sourceto types Country Indicator Year
• 10.
  Research problems Mapping datasources to types What is a type? What is a value? Types are provided on demand Cannot generate all indicator types at once! Representing data source properties as types Physical units, provenance, temporal properties Adapting to schema change Type soundness is relative w.r.t. data source changes
• 11.
  Gamma, The Forgotten Standardtyping judgments Gamma on steroids Γ = …, WB.DataContext WB.DataContext = Countries : delay (…) Country list Reducing delayed context
• 12.
  Research problems Mapping datasources to types What is a type? What is a value? Types are provided on demand Cannot generate all indicator types at once! Representing data source properties as types Physical units, provenance, temporal properties Adapting to schema change Type soundness is relative w.r.t. data source changes
• 13.
  DEMO: XML TypeProvider Working with XML data and adapting to schema change
• 14.
  Related Work Compile-time meta-programming Types generated eagerly, not on demand Dependently typed languages Type-level computation in the IO monad?? Multi-stage computations Focus on performance vs. data access
• 15.
  For more information Upcomingtechnical report Don Syme, et al. Strongly-Typed Language Support for an Information-Rich World Workshop on related topics Data Driven Functional Programming Workshop, Co-located with POPL 2013
• 16.
  Summary Mismatch between dataand types Type providers bridge the gap Development-time, compile-time & run-time Interesting future questions Relative type safety and schema change Capturing meta-data with types
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  Research problems Mapping datasources to types What is a type? What is a value? Types are provided on demand Cannot generate all indicator types at once! Representing data source properties as types Physical units, provenance, temporal properties Adapting to schema change Type soundness is relative w.r.t. data source changes
• 18.
  DEMO: FreeBase TypeProvider Working with chemistry data and units of measure
• 19.
  Structure of aSimple Provider [<TypeProvider>] type SampleTypeProvider(config: TypeProviderConfig) = inherit TypeProviderForNamespaces() // Define new type Samples.GeneratedType let thisAssembly = Assembly.GetExecutingAssembly() let providedType = ProvidedTypeDefinition( ... ) do // Add property 'Hello' that just returns a string ProvidedProperty ( "Hello", typeof<string>, IsStatic = true, GetterCode = fun args -> <@@ Runtime.lookup "Hello" @@>) |> providedType.AddMember // Register the type with the compiler this.AddNamespace(namespaceName, [ providedType ])
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  Compile-Time vs. Run-time TypeProvider Runtime API Provider Accesses Data Generates source Uses Accesses Provided code Executable
• 21.
  Compile-Time vs. Run-time TypeProvider Runtime API Provider Accesses Data Generates source Provided code Executable
• 22.
  Queries in F# Canbe turned to quotations query { for movie in netflix.Titles do where (movie.Name.Contains(search)) select movie } Extensible query language query { for index in Numbers do reverse takeWhile index > 10 }