tour of language landscape

@theburningmonkYan Cui @theburningmonk

@theburningmonk

Hi, my name is Yan Cui.

@theburningmonk

http://bit.ly/1SPNPn7

ZOOZU

VAPA

BOROU

DUMBU

dark shades of blue, red, green & purple

white & some shades of yellow

some shades of green & blue

other shades of green, red & brown

@theburningmonk

“The limits of my language means the limits of my world.”

- Ludwig Wittgenstein

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agenda

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Type Provider Pipes

Statically Resolved TP Implicit Interface Implementation

Borrowed Pointers Dependent Types

Uniqueness Types

Bit SyntaxSignals

Macros

Unit-of-Measure

Actor Model

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Type Provider Pipes



Uniqueness Types

Bit SyntaxSignals

Macros

Unit-of-Measure

Actor Model

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your app

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your app

CSVCSVCSV

CSVCSVXML

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your app

CSVCSVCSV

CSVCSVXML

some service

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your app

CSVCSVCSV

CSVCSVXML

some service

DB

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1. define DTO types2. I/O3. marshal data into DTO4. do useful work

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compilerprovideexternal

data source typed info

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type providers

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intellisensetooltips

…

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intellisense over S3 buckets & objects!

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compile time validation

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no code generation

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R

FunScript AzureAmazon S3

CSVSQLiteSQL Server

WSDL

WorldBank

RegexODATA IKVM

FacebookApiary

XAMLFreebaseHadoop

Oracle

Minesweeper

Don SymePowershell

JSON

Fizzbuzz

Mixin

RSS

MatlabDates

NorthPole

XML

Python

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Don Syme can taste lies.

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Type Provider Pipes



Uniqueness Types

Bit SyntaxSignals

Macros

Unit-of-Measure

Actor Model

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“…a clean design is one that supports visual thinking so

people can meet their informational needs with a

minimum of conscious effort.”

- Daniel Higginbotham (www.visualmess.com)

http://www.visualmess.com

@theburningmonk

Whilst talking with an ex-colleague, a question came up on how to implement the Stable Marriage problem using a message passing approach. Naturally, I wanted to answer that question with Erlang!

Let’s first dissect the problem and decide what processes we need and how they need to interact with one another.

The stable marriage problem is commonly stated as:Given n men and n women, where each person has ranked all members of the opposite sex with a unique number between 1 and n in order of preference, marry the men and women together such that there are no two people of opposite sex who would both rather have each other than their current partners. If there are no such people, all the marriages are “stable”. (It is assumed that the participants are binary gendered and that marriages are not same-sex).From the problem description, we can see that we need:* a module for man* a module for woman* a module for orchestrating the experimentIn terms of interaction between the different modules, I imagined something along the lines of…

how we read ENGLISH

see also http://bit.ly/1KN8cd0

http://bit.ly/1KN8cd0

@theburningmonk




2. top-to-bottom1.left-to-right

how we read ENGLISH



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how we read CODE

public void DoSomething(int x, int y){ Foo(y, Bar(x, Zoo(Monkey())));}



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how we read CODE


2. bottom-to-top

1.right-to-left



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2. top-to-bottom

1.left-to-right

how we read ENGLISH


2. top-to-bottom

1.right-to-left

how we read CODE



@theburningmonk

“…a clean design is one that supports visual thinking so

people can meet their informational needs with a

minimum of conscious effort.”

@theburningmonk

|>

@theburningmonk

how we read CODE

let drawCircle x y radius = radius |> circle |> filled (rgb 150 170 150) |> alpha 0.5 |> move (x, y)



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how we read CODE

let drawCircle x y radius = radius |> circle |> filled (rgb 150 170 150) |> alpha 0.5 |> move (x, y)

2. top-to-bottom1.left-to-right



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let drawCircle x y radius = circle radius |> filled (rgb 150 170 150) |> alpha 0.5 |> move (x, y)



@theburningmonk

Type Provider Pipes



Uniqueness Types

Bit SyntaxSignals

Macros

Unit-of-Measure

Actor Model

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NASA orbiter crashed because one engineer accidentally used miles instead of kilometres

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you’re never too smart to make mistakes

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unit-of-measure

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[<Measure>]type Pence

e.g. 42<Pence>153<Pence>…

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10<Meter> / 2<Second> = 5<Meter/Second>10<Meter> * 2<Second> = 20<Meter Second> 10<Meter> + 10<Meter> = 20<Meter>10<Meter> * 10 = 100<Meter>10<Meter> * 10<Meter> = 100<Meter2>10<Meter> + 2<Second> // error10<Meter> + 2 // error

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@theburningmonk

Type Provider Pipes



Uniqueness Types

Bit SyntaxSignals

Macros

Unit-of-Measure

Actor Model

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Homoiconicity

…homoiconicity is a property of some programming languages in which the program structure is similar to its syntax, and therefore the program’s internal representation can be

inferred by reading the text’s layout…

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code is data data is code

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(let [x 1] (inc x))

see also http://bit.ly/1PpIrjS

http://bit.ly/1PpIrjS

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(let [x 1] (inc x))

=> 2



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list (1 2 3) vector [1 2 3]



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(let [x 1] (inc x))

list



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(let [x 1] (inc x))

symbol



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(let [x 1] (inc x))

vector



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(let [x 1] (inc x))

list



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form : code as data structure



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code data

quote

eval



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quote

(+ 1 2) => 3



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quote

(+ 1 2) => 3 (quote (+ 1 2)) => (+ 1 2)



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quote

(+ 1 2) => 3 (quote (+ 1 2)) => (+ 1 2) ‘(+ 1 2) => (+ 1 2)see also http://bit.ly/1PpIrjS


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eval

‘(+ 1 2) => (+ 1 2) (eval ‘(+ 1 2)) => 3



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macros

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(defmacro assert-equals [actual expected] ‘(let [actual-val# ~actual] (when-not (= actual-val# ~expected) (throw (AssertionError. (str “FAIL in “ ‘~actual “\n expected: “ ‘~expected “\n actual: “ actual-val#))))))



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(assert-equals (inc 1) 2) ; => nil (assert-equals (inc 1) (+ 0 1)) ; => AssertionError FAIL in (inc 1) ; expected: (+ 0 1) ; actual: 2



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(assert-equals (inc 1) 2) ; => nil (assert-equals (inc 1) (+ 0 1)) ; => AssertionError FAIL in (inc 1) ; expected: (+ 0 1) ; actual: 2

huh?? where? what? how?



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(assert-equals (inc 1) (+ 0 1))



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‘(



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expanded at compile time



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(macroexpand '(assert-equals (inc 1) (+ 0 1))) ; => ; (let* [actual-value__16087__auto__ (inc 1)] ; (clojure.core/when-not ; (clojure.core/= actual-value__16087__auto__ (+ 0 1)) ; (throw (java.lang.AssertionError. ; (clojure.core/str ; "FAIL in " (quote (inc 1)) ; "\nexpected: " (quote (+ 0 1)) ; "\n actual: " actual-value__16087__auto__)))))



@theburningmonk

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Type Provider Pipes



Uniqueness Types

Bit SyntaxSignals

Macros

Unit-of-Measure

Actor Model

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GC is great

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runtime cost

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ownership

see also http://bit.ly/1F6WBVD

http://bit.ly/1F6WBVD

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memory safety without GC



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ZERO runtime cost



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safety + speed



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fn foo() { // v has ownership of the vector let v = vec![1, 2, 3]; // mutable binding let mut v2 = vec![]; } // vector is deallocated at the // end of scope, // this happens deterministically



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immutable by default



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// take ownership let v = vec![1, 2, 3];



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// moved ownership to v2 let v2 = v;



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// moved ownership to v2 let v2 = v;

println!("v[0] is {}", v[0]); // error: use of moved value: `v` // println!("v[0] is {}", v[0]); // ^



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fn take(v : Vec<i32>) { // ownership of vector transferred // to v in this scope }



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// moved ownership take(v);



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// moved ownership take(v);

println!("v[0] is {}", v[0]); // error: use of moved value: `v` // println!("v[0] is {}", v[0]); // ^



@theburningmonksee also http://bit.ly/1F6WBVD


@theburningmonk

let me buy your book



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sure thing!



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thanks



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BURN!!! >:D



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but I still need it..

:’(



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borrowing



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// note we're taking a reference, // &Vec<i32>, instead of Vec<i32> fn take(v : &Vec<i32>) { // no need to deallocate the vector // after we go out of scope here }



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// notice we're passing a reference, // &v, instead of v take(&v); // borrow ownership

println!("v[0] is {}", v[0]); // v[0] is 1



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let me borrow your

book



@theburningmonk

sure thing!



@theburningmonk

thanks



@theburningmonk

I’m done, here you go



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thanks



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immutable by default



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fn take(v : &Vec<i32>) { v.push(5); }

let v = vec![]; take(&v); // cannot borrow immutable borrowed // content `*v` as mutable // v.push(5); // ^



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fn take(v : &mut Vec<i32>) { v.push(5); }

let mut v = vec![]; take(&mut v);

println!("v[0] is {}", v[0]); // v[0] is 5



there are 2 rules to BORROWING

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Rule 1.the borrower’s scope must not

outlast the owner



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Rule 2.one of the following, but not both:

2.1 0 or more refs to a resource 2.2 exactly 1 mutable ref



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data race

There is a ‘data race’ when two or more pointers access the same memory location at the same time, where at least one of them is writing, and

the operations are not synchronised.



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data race

a. two or more pointers to the same resourceb. at least one is writingc. operations are not synchronised



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Data Race Conditionsa. two or more pointers to the same resourceb. at least one is writingc. operations are not synchronised

Borrowing Rulesone of the following, but not both:

2.1 0 or more refs to a resource 2.2 exactly 1 mutable ref



@theburningmonksee also http://bit.ly/1F6WBVD


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@theburningmonk

Dependent Types

Uniqueness Types

Bit Syntax

Borrowed Pointers

Type Provider Pipes


Signals

Macros

Unit-of-Measure

Actor Model

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seen generics?aka parametric polymorphism

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List<T>

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List<T>List<int> List<Cat>

List<string>

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what if…

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types that depend on arbitrary values?

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Vect n avector of n elements of type a

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zipWith : (a -> b -> c) -> Vect n a -> Vect n b -> Vect n c

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zipWith f [] [] = [] zipWith f (x :: xs) (y :: ys) = f x y :: zipWith f xs ys

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Type Driven Development

“Make illegal states unrepresentable”

- Yaron Minsky

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Type Provider Pipes



Uniqueness Types

Bit SyntaxSignals

Macros

Unit-of-Measure

Actor Model

@theburningmonk

10,000 hours to be good at something

see also http://bit.ly/1KN7SLq

http://bit.ly/1KN7SLq

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10,000 hours to reach top of an ultra-

competitive field



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the first 20 hours - how to learn anything



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Practice Time

How

goo

d yo

u ar

e



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1.Deconstruct the skill



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1.Deconstruct the skill2.Learn enough to self-correct



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1.Deconstruct the skill2.Learn enough to self-correct3.Remove practice barriers



@theburningmonk

1.Deconstruct the skill2.Learn enough to self-correct3.Remove practice barriers4.Practice at least 20 hrs



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@theburningmonk

learn a new paradigmnot a new syntax

see also http://bit.ly/1IzXVSo

http://bit.ly/1IzXVSo

“Programming languages have a devious influence: they shape our thinking

habits.”

- Edsger W. Dijkstra

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logic programming

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stack-oriented programming

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array programming

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“A language that doesn't affect the way you think

about programming, is not worth knowing.”

- Alan Perlis

@theburningmonksee also http://bit.ly/1IzXVSo

http://bit.ly/1IzXVSo

@theburningmonk

“Learning is an act of creation itself, because something

happens in you that wasn't there before.”

- Alan Kay

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@theburningmonktheburningmonk.comgithub.com/theburningmonk

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