Ethereum – Art Is…

Here is a contract that allows anyone to define what art is. It contains a single set of twelve statements about art. They are encoded as hexadecimal values which are interpreted as sentences in a simple subset of International Art English and displayed by the UI.

 ;; Constant values
 ;; Price base (wei), doubled for each definition up to DEFS-COUNT
 (def 'PRICE-BASE 10)
 ;; Add to the index to get the price base exponent
 ;; Number of definitions
 (def 'DEFS-COUNT 12)
 ;; Range of values for definitions
 (def 'DEF-MIN 0x1)
 (def 'DEF-MAX 0x0F0F0F0F)

 ;; Storage locations
 (def 'artist 0x10)
 (def 'defs-base 0x100)
 (def 'theorists-base 0x200)

 ;; State
 ;; Contract owner/payee
 [[artist]] (caller)

     [action] (calldataload 0)
      (when (= @action "set")
         [index] (calldataload 32)
         [definition] (calldataload 64)
         [price] (exp PRICE-BASE (+ @index 1 PRICE-FACTOR-ADD))
         ;; If the index is in range and the caller paid enough to set it
         (when (&& (>= @definition DEF-MIN)
                   (<= @definition DEF-MAX)
                   (< @index DEFS-COUNT)
                   (= (callvalue) @price))
            ;; Update definition
            [[(+ defs-base @index)]] @definition
            [[(+ theorists-base @index)]] (caller)
            (- (gas) 100) @@artist @price 0 0 0 0

The contract is in lll rather than Serpent this time.

Here’s what the UI looks like.
And here’s what it looks like when a statement is being edited.
The contract allows the statements to be edited but it costs progressively more to do so: the first costs 10 Wei, the third costs 1000 and so on. This ensures that art theorists place a value on their definition, thereby indicating how confident in and/or serious about their definition they are. The higher the value, the less likely it is to be changed by someone else. This combines art theory with behavioral economics.