Web directions code 13 notes

See the tries for the trees
http://www.ﬂickr.com/photos/zoer/2363020211/
Tuesday, 7 May 13

Add fast moving images
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1861
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“A general “law of least effort” applies to cognitive as well as physical
exertion. The law asserts that if there are several ways of achieving the
same goal, people will eventually gravitate to the least demanding course
of action. In the economy of action, effort is a cost, and the acquisition of
skill is driven by the balance of benefits and costs. Laziness is built deep into our nature.”

Tuesday, 7 May 13
Personal experience
Negative experience
Fundamental attribution error

Moore’s law
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every 2 years the number of transistors increases
This has also mapped to hard drives and clock speed.

2008
2011
412 Hz 1 GHz
Dual-Core
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Wirth’s law
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Wirth’s law
Gate’s law
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Wirth’s law
Gate’s law
May’s law
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Wirth’s law
Gate’s law
May’s law
Page’s law
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Offset Moore’s law
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"software is getting slower more rapidly than hardware becomes faster." this was said in 1995 the year java was released.

JS’s moore law?
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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?
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http://upload.wikimedia.org/wikipedia/commons/5/52/Pdp7-oslo-2005.jpeg
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Peter Samson
200 kilohertz
16K

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 basics
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$(“#selector”);
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654321 1110987
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654321 1110987
654321 1110987
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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.

Not function()al
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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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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 effects
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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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function id(x) {
y = 30;
updateDB(y,x);
return x;
}
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Higher order
programming
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[-60, -10, -20].map(Math.abs)[-60, -10, -20].map(Math.abs)
[60, 10, 20]
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[-60, 10, -20].filter(function(x)
{ return x > 0});
[10]
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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 13
December, 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 matters
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Abstract concept
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Higher higher
order programming
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s/Maybe/MaybeMonad
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Chain = bind
>>=
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Standards +
Academia +
Javascript =
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Fantasy land
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It was so named after the infamous bug 94 on the promises spec
Dealing with null.

Free.
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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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Javascript is untyped
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A type system is a tractable syntactic
method for proving the absence of certain
program behaviors by classifying phrases
according to the kinds of values they
compute.
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A type system is a tractable syntactic
method for proving the absence of certain
program behaviors by classifying phrases
according to the kinds of values they
compute.
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tractable easy to control

string -> string
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function(string) {
return string;
}
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[string] -> string
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function add(a,b) {
return a + b;
}
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add(“1”,2)
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REX.W movq rax,[rbp+0x18]
test al,0x1
+
JS
Tuesday, 7 May 13

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