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
(def 'PRICE-FACTOR-ADD 10)
;; 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)
(return
0x0
(lll
{
[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
})
})
}
0x0))
}
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.