ERC20

archetype erc20
​
constant name : string = "mytoken"
​
constant total : int = 1000
with {
  i0: total > 0
}
​
asset allowance {
    allowed : address;
    amount  : int;
} with {
    i2 : amount > 0;
}
​
asset tokenHolder identified by holder {
    holder     : address;
    tokens     : int;
    allowances : allowance collection;
} with {
    i1: tokens >= 0;
    i3: allowances.sum(the.amount) <= tokens;
} initialized by [
  { holder = caller; tokens = total; allowances = [] }
]
​
action dotransfer (dest : pkey of tokenHolder, value : int) {
​
  specification {
    p1 : before.tokenHolder.sum(tokens) = tokenHolder.sum(tokens);
    p2 : let some th = tokenHolder.get(dest) in
         let some bth = before.tokenHolder.get(dest) in
         th.tokens = bth.tokens + value
         otherwise true
         otherwise true;
    p3 : let some thc = tokenHolder.get(caller) in
         let some bthc = before.tokenHolder.get(caller) in
         thc.tokens = bthc.tokens - value
         otherwise true
         otherwise true;
    p4 : let some th = tokenHolder.get(dest) in
         forall t in tokenHolder,
         forall bt in before.tokenHolder,
         t.holder <> th.holder ->
         t.holder <> caller ->
         t.tokens = bt.tokens
         otherwise true;
  }
​
  failif {
    f0 : value < 0;
    f1 : tokenHolder.get(caller).tokens < value
  }
​
  effect {
    tokenHolder.update( tokenHolder.get(dest).holder, { tokens += value });
    tokenHolder.update( caller, { tokens -= value })
  }
}
​