5aed8b3ef5
Functions must be annotated as `stateful` in order to - Update the contract state (using `put`) - Call `Chain.spend` or other primitive functions that cost tokens - Call an Oracle or AENS function that requires a signature - Make a remote call with a non-zero value - Construct a lambda calling a stateful function It does not need to be stateful to - Read the contract state - Call another contract with value=0, even when the remote function is stateful
44 lines
1.4 KiB
Plaintext
44 lines
1.4 KiB
Plaintext
//
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// Dutch auction example
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//
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contract DutchAuction =
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record state = { start_amount : int,
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start_height : int,
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dec : int,
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beneficiary : address,
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sold : bool }
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// Add to work around current lack of predefined functions
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private stateful function spend(to, amount) =
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let total = Contract.balance
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Chain.spend(to, amount)
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total - amount
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private function require(b : bool, err : string) =
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if(!b) abort(err)
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// TTL set by user on posting contract, typically (start - end ) div dec
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public function init(beneficiary, start, decrease) : state =
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require(start > 0 && decrease > 0, "bad args")
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{ start_amount = start,
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start_height = Chain.block_height,
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beneficiary = beneficiary,
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dec = decrease,
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sold = false }
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// -- API
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// We are the buyer... interesting case to buy for someone else and keep 10%
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public stateful function bid() =
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require( !(state.sold), "sold")
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let cost =
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state.start_amount - (Chain.block_height - state.start_height) * state.dec
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require( Contract.balance >= cost, "no money")
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// transaction(SpendTx({recipient = state.beneficiary,
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// amount = cost })) // or self.balance ** burn money **
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spend(state.beneficiary, cost)
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spend(Call.caller, Contract.balance)
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put(state{sold = true})
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