nordic-dev.net/rust
nordic-dev.net/rust
2
0
Fork 0
mirror of https://github.com/rust-lang/rust.git synced 2025-01-28 15:43:21 +00:00
Code Issues Packages Projects Releases Wiki Activity

std: Replace map_vec, map_vec2, iter_vec2 in std::result

Browse Source 
Replace these with three functions based on iterators: collect, fold,
and fold_. The mapping part is replaced by iterator .map(), so the part
that these functions do is to accumulate the final Result<,> value.

* `result::collect` gathers `Iterator<Result<V, U>>` to `Result<~[V], U>`
* `result::fold` folds `Iterator<Result<T, E>>` to `Result<V, E>`
* `result::fold_` folds `Iterator<Result<T, E>>` to `Result<(), E>`
This commit is contained in:
blake2-ppc 2013-08-12 20:24:05 +02:00
parent 6fe4c871f1
commit 88c149195a
2 changed files with 93 additions and 62 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
src/librustc/middle/typeck/infer/combine.rs
View File

@ -68,7 +68,7 @@ use middle::typeck::infer::{InferCtxt, cres, ures};
use middle::typeck::infer::{TypeTrace};
use util::common::indent;
use std::result::{iter_vec2, map_vec2};
use std::result;
use std::vec;
use syntax::ast::{Onceness, purity};
use syntax::ast;
@ -275,9 +275,9 @@ pub fn super_tps<C:Combine>(
// variance.
if vec::same_length(as_, bs) {
iter_vec2(as_, bs, |a, b| {
eq_tys(this, *a, *b)
}).then(|| Ok(as_.to_owned()) )
result::fold_(as_.iter().zip(bs.iter())
.map(|(a, b)| eq_tys(this, *a, *b)))
.then(|| Ok(as_.to_owned()))
} else {
Err(ty::terr_ty_param_size(
expected_found(this, as_.len(), bs.len())))
@ -427,7 +427,8 @@ pub fn super_fn_sigs<C:Combine>(
{
fn argvecs<C:Combine>(this: &C, a_args: &[ty::t], b_args: &[ty::t]) -> cres<~[ty::t]> {
if vec::same_length(a_args, b_args) {
map_vec2(a_args, b_args, |a, b| this.args(*a, *b))
result::collect(a_args.iter().zip(b_args.iter())
.map(|(a, b)| this.args(*a, *b)))
} else {
Err(ty::terr_arg_count)
}
@ -586,8 +587,9 @@ pub fn super_tys<C:Combine>(
(&ty::ty_tup(ref as_), &ty::ty_tup(ref bs)) => {
if as_.len() == bs.len() {
map_vec2(*as_, *bs, |a, b| this.tys(*a, *b) )
.chain(|ts| Ok(ty::mk_tup(tcx, ts)) )
result::collect(as_.iter().zip(bs.iter())
.map(|(a, b)| this.tys(*a, *b)))
.chain(|ts| Ok(ty::mk_tup(tcx, ts)) )
} else {
Err(ty::terr_tuple_size(
expected_found(this, as_.len(), bs.len())))

139
src/libstd/result.rs
View File

@ -18,8 +18,7 @@ use either;
use iterator::Iterator;
use option::{None, Option, Some, OptionIterator};
use vec;
use vec::{OwnedVector, ImmutableVector};
use container::Container;
use vec::OwnedVector;
use to_str::ToStr;
use str::StrSlice;
@ -269,86 +268,76 @@ pub fn map_opt<T, U: ToStr, V>(o_t: &Option<T>,
}
}
// FIXME: #8228 Replaceable by an external iterator?
/// Maps each element in the vector `ts` using the operation `op`. Should an
/// error occur, no further mappings are performed and the error is returned.
/// Should no error occur, a vector containing the result of each map is
/// returned.
/// Takes each element in the iterator: if it is an error, no further
/// elements are taken, and the error is returned.
/// Should no error occur, a vector containing the values of each Result
/// is returned.
///
/// Here is an example which increments every integer in a vector,
/// checking for overflow:
///
/// fn inc_conditionally(x: uint) -> result<uint,str> {
/// fn inc_conditionally(x: uint) -> Result<uint, &'static str> {
/// if x == uint::max_value { return Err("overflow"); }
/// else { return Ok(x+1u); }
/// }
/// map(~[1u, 2u, 3u], inc_conditionally).chain {|incd|
/// assert!(incd == ~[2u, 3u, 4u]);
/// }
/// let v = [1u, 2, 3];
/// let res = collect(v.iter().map(|&x| inc_conditionally(x)));
/// assert!(res == Ok(~[2u, 3, 4]));
#[inline]
pub fn map_vec<T,U,V>(ts: &[T], op: &fn(&T) -> Result<V,U>)
-> Result<~[V],U> {
let mut vs: ~[V] = vec::with_capacity(ts.len());
for t in ts.iter() {
match op(t) {
Ok(v) => vs.push(v),
Err(u) => return Err(u)
pub fn collect<T, E, Iter: Iterator<Result<T, E>>>(mut iterator: Iter)
-> Result<~[T], E> {
let (lower, _) = iterator.size_hint();
let mut vs: ~[T] = vec::with_capacity(lower);
for t in iterator {
match t {
Ok(v) => vs.push(v),
Err(u) => return Err(u)
}
}
return Ok(vs);
Ok(vs)
}
// FIXME: #8228 Replaceable by an external iterator?
/// Same as map, but it operates over two parallel vectors.
/// Perform a fold operation over the result values from an iterator.
///
/// A precondition is used here to ensure that the vectors are the same
/// length. While we do not often use preconditions in the standard
/// library, a precondition is used here because result::t is generally
/// used in 'careful' code contexts where it is both appropriate and easy
/// to accommodate an error like the vectors being of different lengths.
/// If an `Err` is encountered, it is immediately returned.
/// Otherwise, the folded value is returned.
#[inline]
pub fn map_vec2<S, T, U: ToStr, V>(ss: &[S], ts: &[T],
op: &fn(&S,&T) -> Result<V,U>) -> Result<~[V],U> {
assert!(vec::same_length(ss, ts));
let n = ts.len();
let mut vs = vec::with_capacity(n);
let mut i = 0u;
while i < n {
match op(&ss[i],&ts[i]) {
Ok(v) => vs.push(v),
Err(u) => return Err(u)
pub fn fold<T, V, E,
Iter: Iterator<Result<T, E>>>(
mut iterator: Iter,
mut init: V,
f: &fn(V, T) -> V)
-> Result<V, E> {
for t in iterator {
match t {
Ok(v) => init = f(init, v),
Err(u) => return Err(u)
}
i += 1u;
}
return Ok(vs);
Ok(init)
}
// FIXME: #8228 Replaceable by an external iterator?
/// Applies op to the pairwise elements from `ss` and `ts`, aborting on
/// error. This could be implemented using `map_zip()` but it is more efficient
/// on its own as no result vector is built.
/// Perform a trivial fold operation over the result values
/// from an iterator.
///
/// If an `Err` is encountered, it is immediately returned.
/// Otherwise, a simple `Ok(())` is returned.
#[inline]
pub fn iter_vec2<S, T, U: ToStr>(ss: &[S], ts: &[T],
op: &fn(&S,&T) -> Result<(),U>) -> Result<(),U> {
assert!(vec::same_length(ss, ts));
let n = ts.len();
let mut i = 0u;
while i < n {
match op(&ss[i],&ts[i]) {
Ok(()) => (),
Err(u) => return Err(u)
}
i += 1u;
}
return Ok(());
pub fn fold_<T, E, Iter: Iterator<Result<T, E>>>(
iterator: Iter)
-> Result<(), E> {
fold(iterator, (), |_, _| ())
}
#[cfg(test)]
mod tests {
use super::*;
use either;
use iterator::range;
use str::OwnedStr;
use vec::ImmutableVector;
pub fn op1() -> Result<int, ~str> { Ok(666) }
@ -431,4 +420,44 @@ mod tests {
assert_eq!(r.to_either(), either::Right(100));
assert_eq!(err.to_either(), either::Left(404));
}
#[test]
fn test_collect() {
assert_eq!(collect(range(0, 0)
.map(|_| Ok::<int, ()>(0))),
Ok(~[]));
assert_eq!(collect(range(0, 3)
.map(|x| Ok::<int, ()>(x))),
Ok(~[0, 1, 2]));
assert_eq!(collect(range(0, 3)
.map(|x| if x > 1 { Err(x) } else { Ok(x) })),
Err(2));
// test that it does not take more elements than it needs
let functions = [|| Ok(()), || Err(1), || fail!()];
assert_eq!(collect(functions.iter().map(|f| (*f)())),
Err(1));
}
#[test]
fn test_fold() {
assert_eq!(fold_(range(0, 0)
.map(|_| Ok::<(), ()>(()))),
Ok(()));
assert_eq!(fold(range(0, 3)
.map(|x| Ok::<int, ()>(x)),
0, |a, b| a + b),
Ok(3));
assert_eq!(fold_(range(0, 3)
.map(|x| if x > 1 { Err(x) } else { Ok(()) })),
Err(2));
// test that it does not take more elements than it needs
let functions = [|| Ok(()), || Err(1), || fail!()];
assert_eq!(fold_(functions.iter()
.map(|f| (*f)())),
Err(1));
}
}