Nemerle is Notable

Nemerle is notable

Nemerle is notable

Denis Rystsovtwitter.com/rystsov

rystsov.denis@gmail.com

2011

Nemerle is notable

Origin

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Nemerle Experience

Nemerle is notable

EnvironmentManaged compiler written in Nemerle

Visual Studio 2008 plugin with debugger and autocomplete

Free IDE based on Visual Studio Isolated Shell

Sharpdevelop plugin

Mono support

NAnt plugin

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Why not try?

Nemerle is almost a superset ofC#, so if you know C# you canuse Nemerle.

Nemerle is notable

Why not try?

By the way, Nemerle's compilercan compile C# code, so youcan try it on exising C# project

Nemerle is notable

Why not try?

Why not try?

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Part I - use your C# habits

Part I - use your C# habits

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Hello world / C#

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Hello world / Nemerle

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Extension Methods / C#

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Extension Methods / Nemerle

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LINQ / C#

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LINQ / Nemerle

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Object Initialization / C#

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Object Initialization / Nemerle

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Anonymous Types / C#

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Anonymous Types / Nemerle

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Yield return / C#

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Yield return / Nemerle

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Dynamic / C#

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Dynamic / Nemerle

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Type casting / C#

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Type casting / Nemerle

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Try..Catch / C#

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Try..Catch / Nemerle

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Partial / C#

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Partial / Nemerle

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Arrays / C#

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Arrays / Nemerle

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Attention! Wild dinosaur!

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Goto?

What is about..

GOTO?unlike C# Nemerle doesn't support it, but..

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The proper use of goto

The only one legal usage of goto is

exit from nested loops

Nemerle provides a bettersolution � named code blocks

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Named code blocks

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Beyond C#

After this short intro you canwrite apps in Nemerle in C#style.

But Nemerle goes far beyond it

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Desired C# features

Itsupportsthe most desiredfeatures of the nextversions of C# right now

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Part II - desired C# features

Part II - desired C# features

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Object initializers with events

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Painless XML generation

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INotifyPropertyChanged language support

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`Safe navigation' operator

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Design by contract

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Sequence initialization (list comprehension)

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Yield from lambda

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Improved lazy support

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Part III � functional programming

Part III � functionalprogramming (FP)

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What is FP?

Typical signs of FPMonadsType inferencePattern matchingAlgebraic data typesBuilt-in tuple supportLocal (nested) functions

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Nemerle supports FP

Nemerle supports it all

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Type inference

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Local functions

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Built-in tuple support

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Monads

Monad is creational functional programming designpattern that deals with computation creation.

The upcoming C# 5 async/await feature is particularcase of a monad (creation of asynchronouscomputation).

Computation expressions are monads + monoids.

Nemerle supports computation expressions.

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Monads

Consequently Nemerle supportsthe upcoming C# 5async/await feature right nowamong the other monads.

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Example of easy composition of two async methods

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Algebraic data types

Short intro toalgebraic data types

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Algebraic data types

Let's learn ADT by example

Suppose we need to work withexpressions like

a + sin(b)

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Algebraic data type

Of couse we need trees

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OOP approach to trees (class hierarchy)

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FP approach to trees (ADT - algebraic data type)

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Algebraic data type � semantic

After we rewrite OOP code with variant (ADT) weshould consider`Sum' as a constructor of type `Tree'`l',`r' as its params (not a Tree.Sum's �elds)

But if they are params, how get them back from a`Tree' typed object?

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Algebraic data type � Disassembling (pattern matching)

Pattern matching solves this problem. It checks if object isconstructed with constructor speci�ed in a pattern and if it is trueit binds actual parameters of constructor with names of variablesthe pattern.

Let's see on the following example.

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Pretty Printing of `Tree' typed object

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Algebraic data type � OOP vs. FP

OOP

72 SLoC (pretty printing withvisitor pattern)

FP

25 SLoC (pretty printing withpattern matching)

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Variant is OOP enabled algebraic data type

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Pattern matching goes beyond disassembling

Pattern matching can be nested.

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Almost all features are macros

Nemerle seems to be complex,but. . .

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Almost all Nemerle features are macros

Don't worryNemerle is a simple language and almost all features aremacros � parts of standard library, not a language.

Macros is a plugin to compiler. You can write your ownmacros to introduce new language constructs or eDSL.

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Almost all Nemerle features are macros

You've already meet macros inthis presentation, they are. . .

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Almost all Nemerle features are macros

LINQ Object initialization Anonymous typesLate (dynamic) XML-LiteralsINotifyPropertyChanged macro Safe navigationDesign by contract Computation expressionsLazy macro

and even

if while foreach

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Advanced macros

Beside macros copying useful features from anotherlanguages there are macros adding unique features.

One of them is Nemerle.Peg. It is a macro-librarythat allows to describe grammar in the attribute andduring the compilation necessary methods for parsingtext in this grammar will be added to the class.

Also there are some macros supporting designpatterns.

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Nemerle is cool

Nemerle is cool.It was proved.

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Metric

Some metric of using Nemerlein home pet long-term researchproject

uniquation.com formula searchengine

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Metric

Two years ago �rst prototype was rewritten from C# toNemerle in 3 days. Nemerle experience before 0.

Code was reduced by 46%.

Last month a new macro library (Nemerle.Peg) was applyed.

Code was reduced by 15%.

Nemerle is notable

Additional materials

Nemerle on google code

Nemerle site

Sources code of examples shown in this presentation