User:Yeem/BE.180 notes/4-25

Drew Endy: So far, we've talked about controlling systems in time & space.

• One extreme: can run autonomously
• Other: runs entirely on external input

Last class: couple different examples of languages

• "Growing point language"
• "Origami language"
• "Crop circle language"

Today, we're going to cover "growing point language". On Thursday, we'll probably do the crop circle language.

Growing point language

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Figure 1

Person responsible: Daniel Coore, head of computer science in Jamaica

Randomly distributed cells (see figure 1)

• two dimsensional surface
• independent agents
• local information: cell can sense surrounding area r away, but not really far from itself
• want them to make a pattern

Challenge: invent a programming language that allows you to make patterns like this

Detals

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Figure 2

How would you imagine wanting to write such a program, in English? (figure 2)

1. Arbitrarily initiate/start at the leftmost point
2. Create line (L to R)
   1. Material (line)
   2. Phermones (signal)
3. Create lines (up/down), with length
4. etc.

Three points of external information:

1. Point 1 (red)
2. Line 1 (blue)
3. Line 2 (orange)

Program

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Figure 3: directions

Actual program for how "tip" point should move:

(define-growing-point(orient-poly length))

(material polymer)

(size n-width) #controls thickness of line as it grows

(tropism(and(ortho-dir-phermone)

and(dia top-rail)(dia bot-rail)

(actions

(when(length<1=terminate) #stops program when length = 0

(default(propogate;length=length-1) #default behavior; propogates and decrements length

(signal name phermone)

Discussion

Costs

• Memory/logic/state
• Communication
• time