该代码适用于:
let stdin = std::io::stdin();
let mut rdr = csv::Reader::from_reader(stdin);
let mut hmap = HashMap::<String, u64>::new();
rdr.records()
.map(|r| r.unwrap())
.fold((), |_, item| {
// TODO: Is there a way not to have to copy item[col] every time?
let counter = hmap.entry(item[col].to_string()).or_insert(0);
*counter += 1;
});
此代码失败,提示:"无法移出acc
,因为它是borrow 的"
let stdin = std::io::stdin();
let mut rdr = csv::Reader::from_reader(stdin);
let hmap = rdr.records()
.map(|r| r.unwrap())
.fold(HashMap::<String, u64>::new(), |mut acc, item| {
// TODO: Is there a way not to have to copy item[col] every time?
let counter = acc.entry(item[col].to_string()).or_insert(0);
*counter += 1;
acc
});