Transcript Unit 21 - Northwestern University

twenty-one
chance operations
Fortune telling and meditation
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Examples:
Tarot, I Ching, Astrology
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Introduce chance
operations into a system
of signs
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Results are “meaningless”
But we give them meaning
after the fact
Garfinkel’s breaching
experiments
there is no noise
only signal
Chance operations
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Fancy term for “randomness”
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A way of taking your ego out of the loop
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A way of automating decisions you don’t want to make
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Get past your preconceived notions
Creating surprise
Creating juxtapositions that can create new meaning for you
Could you draw a random line?
Generating a terrain for
A way of automating decisions you can’t make
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Interactive art – the artist isn’t there to make the decisions
The Art of Noise
[show
[p → [× 256
[turbulence [× 0.001
p.X p.Y]]]]]
turbulence with a numeric argument
[show
[p → [× 256
[cos [× 10
[turbulence [ ⁄ p 50]]]]]]]
Exquisite corpse
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The surrealists used a variety of
unusual composition techniques
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Automatic writing
Dreams as source material
Chance operations
Why?
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They were followers of Freud
They saw the conscious mind as
representative of the ills of society
(repression, war, exploitation)
Unlock the unconscious
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Escape the sources of repression
Recover a more “natural” state of the
psyche
Open oneself up to the possibility of
delightful coincidence
Source: http://anexquisitecorpse.net/explanation.shtml
The electric corpse
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You now know enough to
write programs to make
exquisite corpse
sentences
We just need one more
primitive procedure
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[random-integer low high]
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Returns a random number
Greater than or equal to
low
And less than high
[define random-get
[list → [get list
[random-integer 0
[length list]]]]]]
[define exquisite-corpse
[→ [list [random-get nouns]
[random-get verbs]
[random-get nouns]]]]
A more elegant version
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It would be more elegant to have
the code read like the grammar for
English
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How would we write the code to
work this way?
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A sentence is a noun phrase and
a verb phrase
A verb phrase is a verb and a
noun phrase
A noun phrase is a determiner
and a noun
Need to write single-word-phrase
And phrase-type
What should a phrase type be
represented as?
[define article
[single-word-phrase
[define adjective
[single-word-phrase
[define noun
[single-word-phrase
[define verb
[single-word-phrase
'[a the some any]]]
'[green heavy …]]]
'[plant table …]]]
'[eat drink …]]]
[define np
[phrase-type article adjective noun]]
[define vp
[phrase-type verb np]]
[define sentence
[phrase-type np vp]]
Writing the driver code
[define single-word-phrase
[words →
[→
[list [random-get words]]]]]
[define phrase-type
[subphrases ... →
[→
[apply append
[map [call :
proc → [proc]]
subphrases]]]]]
Wow, man, deep…
Meta development environment,
version 1.0.1528.32705
Copyright © 2003 Northwestern University.
► «Load the code»
► [sentence]
[a green rain kill some green dubya]
► [sentence]
[any carnivorous rain drink any carnivorous
plant]
► [sentence]
[some heavy coffee drink some carnivorous cup]
► [sentence]
[a heavy coffee drink a magnificent table]
► [sentence]
[the heavy cup defenestrate some carnivorous
coffee]
►
► [sentence]
[a magnificent cup eat some green plant]
► [sentence]
[the magnificent rain bite some green coffee]
John Cage, 4’33”
(excerpt)
what did you hear?
What the heck was that about?
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Cage wanted people to listen to silence around
them with the attitude they bring to a concert
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Listening is an active process of making meaning
We can find rhythms in the sound of someone
speaking
Or hear harmony in a power drill
Cage believed these could be just as musical as
a symphony
Okay, but what does this have to do
with chance operations?
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Silence isn’t silent
It’s filled with sound
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People walking down the hall
The vibration of the HVAC units
People giggling
People shifting uncomfortably in their chairs
All of these can be heard as music
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If you don’t believe me
Try sampling it and giving it to a DJ
Random compositions
Coding random algorithms
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How do we code something
like this?
Each image is
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A set of boxes
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Of random size
In random position
With random color
So we need to make a bunch
of random boxes
Then group them
Let’s start with making a
random color …
Random colors
[define random-color
[→ [color [random-integer 0 255]
[random-integer 0 255]
[random-integer 0 255]
[random-integer 0 255]]]]
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If you specify a fourth color component, it’s used
as the opacity level or “alpha” channel
A cleaner version
[define random-color
[with component = [→ [random-integer 0 255]]
[→ [color [component]
[component]
[component]
[component]]]]
Making a random box
[define random-box
[max-width max-height →
[with random-point = [→ [point [random-integer 0 max-width]
[random-integer 0 max-height]]]
[box [random-point]
[random-point]]]]]
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Box can be called two corners (points) as arguments
Abstracting it to other shapes
[define random-shape
[shape max-width max-height →
[with random-point = [→ [point [random-integer 0 max-width]
[random-integer 0 max-height]]]
[shape [random-point]
[random-point]]]]]
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While we’re at it, we might as well put in the ability to
make other kinds of shapes (like ellipses) too
Making a random box
[define boxer “Return a randomly colored random box”
[→ [paint [random-color]
[random-shape box 200 200]]]]
And now a bunch of boxes
[define boxes “A picture with box-count random boxen”
[box-count → [apply group
[iterate boxer box-count]]]]
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And we need a helper procedure:
[define iterate “Call φ count times and return a list of the results.”
[φ count → [up-to count
[call : ignore → [φ]]]]]
Running it
► [boxes 5]
► [boxes 10]
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Stochastic grammars
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The electric corpse code was
random and recursive
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But the randomness was just
in word selection
Not in the grammar
To change the grammar, we
need to randomly select
procedures
[define random-call
[proc-list args ... →
[apply [random-get proc-list]
args]]]
[define verb-phrase
[→ [random-call
[list verb
[phrase-type verb
noun-phrase]
[phrase-type verb
noun-phrase
noun-phrase]]]]]
Random (and dull, and colorless)
stained-glass windows
[define hsplit
[width height → [check valid-box?
[recenter
[stack-left [random-box [ ⁄ width 2]
height]
[random-box [ ⁄ width 2]
height]]]]]]
[define vsplit
[width height → [check valid-box?
[recenter
[stack-top [random-box width
[ ⁄ height 2]]
[random-box width
[ ⁄ height 2]]]]]]]
[define box-operators
[list hsplit vsplit]]
«Add more to taste»
[define random-box
[width height →
[if [or [< width 25]
[< height 25]]
[box width height]
[random-call box-operators width height]]]]
Trying it
► [random-box 128 128]
► [define box-operators
[list box vsplit vsplit vsplit hsplit hsplit]]
► [random-box 256 256]
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