...with this method brings the risk
* that someone may use both the old and the new allowance by unfortunate
* transaction ordering. One possible solution to mitigate this race
* condition is to first reduce the spender's allowance to 0 and set the
* desired value afterwards:
...
...的是,Kleinberg等人\[ [5](http://Jon Kleinberg, Sendhil Mullainathan, and Manish Raghavan. 2017. Inherent Trade-Offs in the Fair Determination of Risk Scores. In Proceedings of the 8th Innovations in Theoretical Computer Science Conference (ITCS ’17).)\]证明**没有机制能够**实现**最...
...
```
/// This DB is a schematized RocksDB wrapper where all data passed in and out are typed according to
/// [`Schema`]s.
#[derive(Debug)]
pub struct DB {
inner: rocksdb::DB,
}
impl DB {
/// Reads single record by key.
pub fn get(&self, schema_key: &S::Key) -> Result { //从数据...
...uint sum){
// Expression that computes data passed in as parameters
// and does not read or modify state
sum = num1 + num2;
}
}
```
输出:
sum = 15
### 为什么要将函数标记为view或pure?
Gas 优化:Gas 消耗只在交易触发时生效,状态被修改时触...