Language Integrated Query in Rust.

functional, linq


Linq in Rust

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Language Integrated Query in Rust (created by declarative macros).

This project is under development! API might be changed.

Quick Start

This is an example:

use linq::linq;
use linq::Queryable;

fn try_linq_methods() {
    let x = 1..100;
    let mut y: Vec<i32> = x.clone().filter(|p| p <= &5).collect();
    y.sort_by_key(|t| -t);
    let y: Vec<i32> = y.into_iter().map(|t| t * 2).collect();
    let e: Vec<i32> = x
        .where_by(|p| p <= &5)
        .order_by(|p| -p)
        .select(|p| p * 2)
    assert_eq!(e, y);

fn try_linq_expr() {
    let x = 1..100;
    let mut y: Vec<i32> = x.clone().filter(|p| p <= &5).collect();
    y.sort_by_key(|t| -t);
    let y: Vec<i32> = y.into_iter().map(|t| t * 2).collect();
    let e: Vec<i32> =
        linq!(from p in x.clone(), where p <= &5, orderby -p, select p * 2).collect();
    assert_eq!(e, y);

If you are familier with LINQ in C#, you will find this is easy to use.


The two imports is necessary:

use linq::linq;         // for `linq!` macro
use linq::iter::Enumerable;    // for LINQ methods and `linq!` macro


The trait linq::Queryable supports LINQ methods on Iterator. You can find the correspondences below.

  • Normal items mean they are builtin methods of Iterator in std.
  • Bold items mean they are implemented in this project. You can find them in module linq::iter (but they are private so that you can't import them).
  • Italic items mean they are not in roadmap. Happy for your suggestions.

  • where => where_by => filter
  • select => map
  • select_many => select_many_single, select_many
  • skip
  • skip_while
  • take
  • take_while
  • join
  • group_join
  • concate => chain
  • order_by
  • order_by_descending
  • then_by
  • then_by_descending
  • reverse => rev
  • group_by
  • distinct
  • union
  • intersect
  • except
  • first => next
  • single
  • element_at => nth
  • all
  • any
  • contains
  • count
  • sum
  • product
  • min
  • max
  • average
  • aggregate => fold


The query expression begins with from clause and ends with select clause. Use , to seperate every clause.

linq!(from x in coll, select x)

Now we supports these keywords:

  • from
    • from (select_many_single)
    • zfrom (select_many)
  • in
  • select
  • where
  • orderby
  • descending
  • group_by
  • more...


from <id> in <iter expr>,

Also you can enumerate elements of each set in the collection (Attention: for this type, you can't access the value that is in the first from clause in select clause):

let x = 1..5;
let y = vec![0, 0, 1, 0, 1, 2, 0, 1, 2, 3];
let e: Vec<i32> = linq!(from p in x.clone(), from t in 0..p, select t).collect();

assert_eq!(e, y);

If you want to zip or enumerate value-pairs of two sets, use zfrom for the second from:

let x = 1..5;
let y = vec![
    (1, 0),
    (2, 0),
    (2, 1),
    (3, 0),
    (3, 1),
    (3, 2),
    (4, 0),
    (4, 1),
    (4, 2),
    (4, 3),
let e: Vec<_> = linq!(from p in x.clone(), zfrom t in 0..p, select (p,t)).collect();

assert_eq!(e, y);

The expression in zfrom recieve the cloned value in the first from, and the elements in two sets will be cloned for select clause.


while <expr>,

You can use where clause in single-from query, and the expression will recieve a variable named the id in from clause. The expression need to return a boolean value.


orderby <expr>,
orderby <expr>, descending,

You can use orderby clause in single-from query. This query will collect the iterator, and sort them by the expression, then return the new iterator.


We need more unit-test samples. If you have any ideas, open issues to tell us.

Since the expression procedural macros is not stable, I only create macros by declarative macros.

$ cargo test