See the tries for the trees

http://www.flickr.com/photos/zoer/2363020211/

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3Tuesday, 7 May 13

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Add fast moving imagesTuesday, 7 May 13

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Halo effect

1861

Tuesday, 7 May 13“A general “law of least effort” applies to cognitive as well as physicalexertion. The law asserts that if there are several ways of achieving thesame goal, people will eventually gravitate to the least demanding courseof action. In the economy of action, effort is a cost, and the acquisition ofskill is driven by the balance of benefits and costs. Laziness is built deep into our nature.”

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Personal experienceNegative experienceFundamental attribution error

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Moore’s lawTuesday, 7 May 13

every 2 years the number of transistors increasesThis has also mapped to hard drives and clock speed.

2008

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2008

2011

412 Hz 1 GHzDual-Core

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Wirth’s lawTuesday, 7 May 13

Wirth’s lawGate’s law

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Wirth’s lawGate’s lawMay’s law

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Wirth’s lawGate’s lawMay’s lawPage’s law

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Offset Moore’s lawTuesday, 7 May 13 "software is getting slower more rapidly than hardware becomes faster." this was said in 1995 the year java was released.

JS’s moore law?Tuesday, 7 May 13

As javascript get engines get faster, developers will increase double the size of their libraries every 2 years.This is 2010 to 2013, so it almost lines up.

More complex?Tuesday, 7 May 13

http://upload.wikimedia.org/wikipedia/commons/5/52/Pdp7-oslo-2005.jpeg

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Peter Samson

200 kilohertz

16K

Well, Why?Tuesday, 7 May 13

Constraints drive creativity

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The Somebody Else's Problem Field is a field running on the principle that if something is identified to be somebody else's problem, the brain will edit it out of the person's vision. - Adams

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We have invented phrases that our somebody elses problem’

Ship it. premature optimization...

Back to basicsTuesday, 7 May 13

$(“#selector”);

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BigO

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O(n)Tuesday, 7 May 13

654321 1110987

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654321 1110987

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O(1)Tuesday, 7 May 13

654321 1110987

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654321 1110987

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O(n^2)Tuesday, 7 May 13

654321 1110987

654321 1110987

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654321 1110987

654321 1110987

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O(logn)Tuesday, 7 May 13

10

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104

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104

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10

4

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10

4

15

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10

4

15

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10

4 15

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10

4 15

2 5 11 25

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104

D Y

4O 4N

T A

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o(K) complexity based on lenght of key, not the data. Kind of neat.

O(n log n)

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similar to o n log n but every time we half the work, we need to iterate through a constant.

FunctionalTuesday, 7 May 13

FunctionalTuesday, 7 May 13

Not function()alTuesday, 7 May 13

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λx.x

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(λx.x) y

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(λx.x) 5

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(λx.x) 5

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5

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Maths is not programming!

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Lambda { |x| x }x => x

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λx. λy .( x + y)

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λy .( 5 + y)

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First class functions!

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function(x) { function(y) { return x + y; }}

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1930

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1975

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Although it was written in some academic papers earlier.

(define (add a) (lambda (b) (+ a b)))

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Side effectsTuesday, 7 May 13

(λx.x) 5

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x => 5

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Referential transparency

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Was actually a term phrased by a philisopher quine.

1960

Change reference. Same context.

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I drank some delicious <>

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I drank some delicious alcohol from scotland.

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I drank some delicious scotch.

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function id(x) { return x;}

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10 + id(5);

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10 + 5;

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function id(x) { y = 30; updateDB(y,x); return x;}

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Sanity

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Higher order programming

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Map

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[-60, -10, -20].map(Math.abs)[-60, -10, -20].map(Math.abs)

[60, 10, 20]

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Filter

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[-60, 10, -20].filter(function(x) { return x > 0});

[10]

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Reduce

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[10, 20,30] .reduce(function(seed, x) { return seed + x }, 0);

60

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1 2 3 4

f(0, 1)

0+1

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1 2 3 4

f(1, 2)

1+2

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1 2 3 4

f(3, 3)

3+3

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1 2 3 4

f(6, 4)

6+4

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Tuesday, 7 May 13December, 2004.

Jeffrey Dean

Jeff Dean puts his pants on one leg at a time, but if he had more legs, you would see that his approach is O(log n).

interface Func<A, B> {

B apply(A x);}

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b = 1;

new Func<Integer, Integer>() {public Integer apply(Integer x) { return x + b; }}

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Syntax mattersTuesday, 7 May 13

Abstract conceptTuesday, 7 May 13

Higher higher order programming

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MonadsTuesday, 7 May 13

s/Maybe/MaybeMonadTuesday, 7 May 13

Chain = bind

>>=

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Of = return

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3 Laws.

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Standards +Academia +Javascript =

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Fantasy landTuesday, 7 May 13

It was so named after the infamous bug 94 on the promises spec

Dealing with null.

Free.Tuesday, 7 May 13

By adhering to these specs we start go get some things for free.For example in my previous maybe example i wrote map. We don’t actually have to do that. It can be implmented for us. Same with a whole host of functions Lift for example which takes a function and runs it in the monadic context.Again we don’t have to worry about writing any of this, we get it for free.

We get assurances to an extent that these operations will run. Regardless of where or what the monad is dealing with.Just freedom. Is this not the idea of the lazy developer and comforms to DRY, LRU etc etc etc

Unfortuantly we can not get 100% assurance if we were to do this, we would need to rely on another concept from the early computer science days...

Types

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Types can take this concept even further.We don’t have to worry about people doing stupid things with our code as we can remove this ability for them

Still need tests

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Tests are slow

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Just less

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Javascript is untypedTuesday, 7 May 13

Sort ofTuesday, 7 May 13

1 TypeTuesday, 7 May 13

Value Tuesday, 7 May 13

A type system is a tractable syntacticmethod for proving the absence of certainprogram behaviors by classifying phrases

according to the kinds of values theycompute.

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A type system is a tractable syntacticmethod for proving the absence of certainprogram behaviors by classifying phrases

according to the kinds of values theycompute.

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tractable easy to control

A type system is a tractable syntacticmethod for proving the absence of certainprogram behaviors by classifying phrases

according to the kinds of values theycompute.

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15 + 5

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a -> a

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a -> a -> a

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string -> string

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function(string) { return string;}

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[a] -> a

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[string] -> string

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Sanity

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function add(a,b) { return a + b;}

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add(1,2)

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add(“1”,2)

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REX.W movq rax,[rbp+0x18] test al,0x1

+JS

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ASM.JS

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Tuesday, 7 May 13