McKinney Gosu2

8/12/2019 McKinney Gosu2

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Introduction to Gosu

A New Language for the JVMfrom ---------------

Scott McKinney

Guidewire [email protected]

www.gosu-lang.com


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Todays Discussion

Background Highlights Open Type System Language Features Tools Q&A


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Background

Guidewire Provide large scale, highly configurable applications Gosu enables unified configuration of customer facing resources:

Rules, Workflows, Web pages, Messaging, Web-services, Tests, etc. Language History(2002 present)

No statically typed, embeddable scripting language available Started small as a rule expression language Evolved slowly: Scripting!OOP!Open Type Sys!Bytecode

Roots Influenced by Java, C#, EcmaScript, Ruby, Pascal Static type system an absolute requirement, esp. for tooling Ideals: Pragmatic, Versatile, Professional


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Highlights


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Type Information

Types

Type Loaders

Type System Type System

TypeLoader 1 TypeLoader 2 . . . TypeLoader N

Type 2Type 1 Type N. . .

TypeInfo

Type System Structure

Open

API

Feature Information PropertyInfo MethodInfoConstructorInfo AnnotationInfo


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Open API

ITypeLoaderIType getType( String name )

. . .

IType

ITypeInfo getTypeInfo()

. . .

ITypeInfo

List getProperties()

List getMethods()

List getConstructors()

. . .

IMethodInfo

IMethodCallHandler getCallHandler()

. . .

IMethodCallHandler

Object handleCall( Object ctx, Object args )

. . .


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Included Types

Gosu provides several kinds of types in the

current open source release. These include:

Classes, Interfaces, Enums Enhancements Programs Templates Blocks/Closures XSD / XML Web Services / WSDL Dynamic Type*


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Language Features


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Obligatory Hello World

Brace for it


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Hello World

!"#$%& ()*++, -,"+./(0 Gosu runsPrograms

No boilerplate class No main() method More on programs later> gosu Hello.gsp)*++, -,"+./

1

More on Command Line Gosu

later

Hello.gsp


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Back to Langauge Features


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Object Oriented

Superset of Javas OO capabilities Fullycompatiblew/ Java

Single class, multiple interface inheritiance

Composition/Delegation support Properties Annotations Enhancements(add behavior to existing types) Anonymous types with variable capture


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fields constructors methods properties inner types

Class Structure

!23425*.*6,

78*892:2;7%#+;

:2"?$26* @ A%"#$53,$8%"73%&0 ;;;

B7$3%#,$B,,&0 ;;;

!",!*"%C5*%D26*&0

3+288E$$*" ;;;F

!23425*keyword same as Java 78*8keyword = Java import 3+288public by default


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Programs

Gosu executesPrograms/Scripts No more boilerplateclass with static main() Can be a simple expressionor Can define any number of statements Can define functions and properties Can define classes, inner classes, and closures Type-safe access to command linearguments


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Programs

78*892:2G;8H#$5;I="26*

78*892:2;2H%;J*3%2$5+*

varframe = newMyFrame()

showMyFrame()

functionshowMyFrame() {

frame.Visible = true

}

classMyFrame extendsJFrame{

construct() {super( "Hello")

DefaultCloseOperation = DISPOSE_ON_CLOSE

Bounds = newRectangle( 100, 100, 100, 100 )

}

}

Mix statementswith

Functionsand Classes


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Templates

Are types e.g., 3,6;B,,;A,6*K*6!+2%* Support JSP/ASP-style syntax: LMN LMON *%3 Support P>syntax too Declare parameters: LMQ !2"268& G@ A%"#$5 0 M1 Can be used anywhere Are supported in String Literals


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Templates

LM 78*892:2;7%#+;R2%*M1

LMQ !2"268&G @ A%"#$50 M1

K*6!+2%* %*G%

LM #B& G;)28S,$%*$%0 > M1E$:#8#T+* %*6!+2%* %*G%

LM F M1

LMUU 3,66*$% UUM1

KV* !2"26 #8@ P>GF

MyTemplate.gstWW J*$.*" .#"*3%+C %, A%"#$5

:2"8%" O

XCK*6!+2%*;"*$.*"K,A%"#$5& (V*++,(0

WW J*$.*" %, H"#%*"

XCK*6!+2%*;"*$.*"& ?H"#%*"N (V*++,(0

WW Y6T*..*. #$ 2 A%"#$5 +#%*"2+

:2"8%" O

(KV* .2%* #8 P>$*HR2%*&0F(

Usage:


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Generics

Reified!:2"B,, O $*H=,,LA%"#$51

!"#$%& B,, !"#$%&=,,LA%"#$510 WW %"7*/

Array-style Variance (no wildcards, easy to understand!):2"+ @


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Enhancements

!23425* .*6,

*$V2$3*6*$%XC ;;; F

F

*;5;N

:2"+#8% O >(\2832+(N (I2:2(N (],87(F

+#8%;!"#$& ^ * U1 !"#$%& * 0 0

Add methodsand properties to existing types (including Java) Look and feel like a class, implicit this reference Fully support generics Dont modify existing class;just type information Statically dispatched Cant add state no fieldsallowed


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Closures/Blocks

:2"+#8% O >(\2832+(N (I2:2(N (],87(F

WW S,++*3%#,$8 H#%V T+,348 &2$. *$V2$3*6*$%80;;;

:2"+#8%_ O +#8%;62!& ^ * U1 *;+*$5%V&0 0

Anonymous functions declared inline Can be either expressions or statement listsArgument and return types inferredbased on contextTrue closures with captured variables Invoked like normal functions Covarianceon return types, contravarianceon argument types

Lets turn a list of Strings into a list of their lengths . . .

WW KV* .*3+2"2%#,$ 8#%* +,,48 +#4*@B7$3%#,$62!L`1& 62!!*"&*+% @ K0@` 0 @ ; ; ; F


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Type Inference

:2"+#8%_ @


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Composition/Delegation

Composition in Gosu

WW A26!+* X#G#$ #$%*"B23*

!7T+#3#$%*"B23*ES+#!T,2".\2"%

>T,,+*2$ 32$S,!C&0a

:,#. 3,!C&0a

T,,+*2$ 32$\28%*&0a

:,#. !28%*&0a; ; ;

F

3+288XC-#$.,H *G%*$.8-#$.,H #6!+*6*$%8ES+#!T,2".\2"%

>

.*+*52%*?3+#!T,2".\2"% "*!"*8*$%8ES+#!T,2".\2"%;;;

F

.*+*52%*keyword "*!"*8*$%8clause specifies interfaces, owning class must declare Compiler automatically dispatches to delegates implementation Otherwise behaves just like a field A single delegate can represent multiple interfaces


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More Language Features

Context sensitive eval()support (in a static language? really!) Using-statement supports RAII(Resource Acquisition Is Initialization) Map and Collection initializationsyntax Object initializersyntax Extensive interval supporte.g., 1..10 Enhanced switch-statement (any type, any expression) Smarter for-statement(handle more types, provides index) Associative arraysyntax for dynamic access to properties Null short-circuitin property access expressions No checked exceptions! Etc.


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Tools!!!

In our view:

A professional, general purpose language is impractical without full-featuredIDE support

The larger the project, the greater the pressure on tools Huge productivity gains via build-time type-safety, editor feedback, codecompletion, navigation, usage searching, and refactoringare not achievable

without the ability to perform solid static analysis

Good news:

Gosus type system enables a rich set of static analysis tools Weve been busy


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Eclipse Plug-in

Full-Featured Syntax coloring Instant feedback as you type Code completion Code navigation Member Usage Search Type Usage Search Refactoring Hover text Structure views Occurrence highlighting Full featured debugger


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Eclipse Plug-in


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REPL Command Line


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Q&A

McKinney Gosu2

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