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@thealmarty
Last active Sep 17, 2019
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A simplified token contract written in Liquidity, for deployment in the Tezos ledger.
type account = {
balance : nat;
allowances : (address, nat) map;
}
type storage = {
accounts : (address, account) big_map;
version : nat;
totalSupply : nat;
name : string;
symbol : string;
owner : address;
}
let get_account (a, (accounts : (address, account) big_map)) =
match Map.find a accounts with
| None -> { balance = 0p; allowances = Map [] }
| Some account -> account
let perform_transfer
(from, dest, tokens, storage) =
let accounts = storage.accounts in
let account_sender = get_account (from, accounts) in
let new_account_sender = match is_nat (account_sender.balance - tokens) with
| None ->
failwith ("Not enough tokens for transfer", account_sender.balance)
| Some b -> account_sender.balance <- b in
let accounts = Map.add from new_account_sender accounts in
let account_dest = get_account (dest, accounts) in
let new_account_dest =
account_dest.balance <- account_dest.balance + tokens in
let accounts = Map.add dest new_account_dest accounts in
[], storage.accounts <- accounts
let%entry transfer (dest, tokens) storage =
perform_transfer (Current.sender (), dest, tokens, storage)
let%entry multiTransfer list_of_transfers storage =
List.fold (fun ((dest, tokens), (_ops, storage)) ->
perform_transfer (Current.sender (), dest, tokens, storage)
) list_of_transfers ([], storage)
let%entry approve (spender, tokens) storage =
let account_sender = get_account (Current.sender (), storage.accounts) in
let account_sender =
account_sender.allowances <-
if tokens = 0p then
Map.remove spender account_sender.allowances
else
Map.add spender tokens account_sender.allowances in
let storage = storage.accounts <-
Map.add (Current.sender ()) account_sender storage.accounts in
[], storage
let%entry transferFrom (from, dest, tokens) storage =
let account_from = get_account (from, storage.accounts) in
let new_allowances_from =
match Map.find dest account_from.allowances with
| None -> failwith ("Not allowed to spend from", from)
| Some allowed ->
match is_nat (allowed - tokens) with
| None ->
failwith ("Not enough allowance for transfer", allowed)
| Some allowed ->
if allowed = 0p then
Map.remove dest account_from.allowances
else
Map.add dest allowed account_from.allowances in
let account_from = account_from.allowances <- new_allowances_from in
let storage = storage.accounts <-
Map.add from account_from storage.accounts in
perform_transfer (from, dest, tokens, storage)
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