6.4. Boost module for LINQ

The LINQ_BOOST module extends LINQ with pipe-friendly macros using underscore syntax for inline predicates and selectors. Expressions like arr |> _where(_ > 3) |> _select(_ * 2) provide concise functional pipelines.

See also LINQ for the full set of query operations. See LINQ — Language-Integrated Query for a hands-on tutorial.

All functions and symbols are in “linq_boost” module, use require to get access to it.

require daslib/linq_boost

Example:

require daslib/linq
    require daslib/linq_boost

    [export]
    def main() {
        var src <- [iterator for (x in range(10)); x]
        var evens <- _where(src, _ % 2 == 0)
        for (v in evens) {
            print("{v} ")
        }
        print("\n")
    }
    // output:
    // 0 2 4 6 8

6.4.1. Call macros

_distinct_by

implements _distinct_by(iterator, expression) shorthand notation that expands into distinct_by(iterator, $(_) => expression).

_none

implements _none(iterator, expression) shorthand notation that expands into none(iterator, $(_) => expression).

_right_join

implements _right_join(srca, srcb, on, result) shorthand notation that expands into right_join(srca, srcb, keya, keyb, result).

_select_many_2

Stage 2 of _select_many (see above). The collection selector’s parameter is now typed, so its body — and hence its element type — is inferred. Read that element type, inject it onto the result selector’s SECOND parameter, and expand into select_many_pair.

_union_by_to_array

implements _union_by_to_array(iterator1, iterator2, expression) shorthand notation that expands into union_by_to_array(iterator1, iterator2, $(_) => expression).

_min_max_average_by

implements _min_max_average_by(iterator, expression) shorthand notation that expands into min_max_average_by(iterator, $(_) => expression).

_order_by_descending_to_array

implements _order_by_descending_to_array(iterator, expression) shorthand notation that expands into order_by_descending_to_array(iterator, $(_) => expression).

_union_by

implements _union_by(iterator1, iterator2, expression) shorthand notation that expands into union_by(iterator1, iterator2, $(_) => expression).

_group_join

implements _group_join(srca, srcb, on, result) shorthand — C# GroupJoin (outer).

_left_join

implements _left_join(srca, srcb, on, result) shorthand notation that expands into left_join(srca, srcb, keya, keyb, result).

_except_by

implements _except_by(iterator1, iterator2, expression) shorthand notation that expands into except_by(iterator1, iterator2, $(_) => expression).

_group_by_lazy_to_array

implements _group_by_lazy_to_array(iterator, key) shorthand notation that expands into group_by_lazy_to_array(iterator, $(_) => key). Returns an array<tuple<key; array<elem>>> instead of an iterator.

_order_by

implements _order_by(iterator, expression) shorthand notation that expands into order_by(iterator, $(_) => expression).

_select_to_array

implements _select_to_array(iterator, expression) shorthand notation that expands into select_to_array(iterator, $(_) => expression).

_where

implements _where(iterator, expression) shorthand notation that expands into where_(iterator, $(_) => expression).

_distinct_by_to_array

implements _distinct_by_to_array(iterator, expression) shorthand notation that expands into distinct_by_to_array(iterator, $(_) => expression).

_group_by_to_array

implements _group_by_to_array(iterator, key) shorthand notation that expands into group_by_lazy_to_array(iterator, $(_) => key).

_cross_join

implements _cross_join(srca, srcb, result) shorthand notation that expands into cross_join(srca, srcb, result). 3-arg form with no on lambda — every (TA, TB) pair surfaces. Use _where after the cross to filter; that’s the explicit-shape inner join.

_take_while

implements _take_while(iterator, expression) shorthand notation that expands into take_while(iterator, $(_) => expression).

_max_by

implements _max_by(iterator, expression) shorthand notation that expands into max_by(iterator, $(_) => expression).

_skip_while

implements _skip_while(iterator, expression) shorthand notation that expands into skip_while(iterator, $(_) => expression).

_order_by_to_array

implements _order_by_to_array(iterator, expression) shorthand notation that expands into order_by_to_array(iterator, $(_) => expression).

_unique_by_to_array

implements _unique_by_to_array(iterator, expression) shorthand notation that expands into unique_by_to_array(iterator, $(_) => expression).

_intersect_by

implements _intersect_by(iterator1, iterator2, expression) shorthand notation that expands into intersect_by(iterator1, iterator2, $(_) => expression).

_select_many

Stage 1 of the correlated SelectMany sugar — _select_many(src, $(o) => coll, $(o, x) => result).

_select

implements _select(iterator, expression) shorthand notation that expands into select(iterator, $(_) => expression).

_sequence_equal_by

implements _sequence_equal_by(iterator1, iterator2, expression) shorthand notation that expands into sequence_equal_by(iterator1, iterator2, $(_) => expression).

_not_in

implements _not_in(element, subquery) shorthand notation that expands into !contains(subquery, element).

_having

implements _having(iterator, expression) shorthand notation that expands into having_(iterator, $(_) => expression).

_all

implements _all(iterator, expression) shorthand notation that expands into all(iterator, $(_) => expression).

_min_max_by

implements _min_max_by(iterator, expression) shorthand notation that expands into min_max_by(iterator, $(_) => expression).

_full_outer_join

implements _full_outer_join(srca, srcb, on, result) shorthand notation that expands into full_outer_join(srca, srcb, keya, keyb, result).

_long_count

implements _long_count(iterator, expression) shorthand notation that expands into long_count(iterator, $(_) => expression).

_min_by

implements _min_by(iterator, expression) shorthand notation that expands into min_by(iterator, $(_) => expression).

_order_by_keys

implements _order_by_keys(iterator, $(x) => (k1, k2, …), descMask) — multi-key order with per-key direction. Expands into order_by_keys(iterator, key-lambda, descMask).

_any

implements _any(iterator, expression) shorthand notation that expands into any(iterator, $(_) => expression).

_in

implements _in(element, subquery) shorthand notation that expands into contains(subquery, element).

_where_to_array

implements _where_to_array(iterator, expression) shorthand notation that expands into where_to_array(iterator, $(_) => expression).

_having_to_array

implements _having_to_array(iterator, expression) shorthand notation that expands into having_to_array(iterator, $(_) => expression).

_count

implements _count(iterator, expression) shorthand notation that expands into count(iterator, $(_) => expression).

_join

implements _join(srca, srcb, on, result) shorthand notation that expands into join(srca, srcb, keya, keyb, result).

_order_by_keys_to_array

implements _order_by_keys_to_array(iterator, $(x) => (k1, k2, …), descMask) shorthand notation that expands into order_by_keys_to_array(iterator, key-lambda, descMask).

_group_by

implements _group_by(iterator, key) shorthand notation that expands into group_by_lazy(iterator, $(_) => key) — same backing function as _group_by_lazy. In-memory both names are aliases:

_except_by_to_array

implements _except_by_to_array(iterator1, iterator2, expression) shorthand notation that expands into except_by_to_array(iterator1, iterator2, $(_) => expression).

_unique_by

implements _unique_by(iterator, expression) shorthand notation that expands into unique_by(iterator, $(_) => expression).

_group_by_lazy

implements _group_by_lazy(iterator, key) shorthand notation that expands into group_by_lazy(iterator, $(_) => key). Yields one tuple<key; array<elem>> per bucket — IGrouping shape, suitable for in-memory per-group processing (top-N per group, group-scoped filtering, grouped JSON emission). See spec history/dasSQLITE/API_REWORK.md "### 19-group_by".

_order_by_descending

implements _order_by_descending(iterator, expression) shorthand notation that expands into order_by_descending(iterator, $(_) => expression).

_intersect_by_to_array

implements _intersect_by_to_array(iterator1, iterator2, expression) shorthand notation that expands into intersect_by_to_array(iterator1, iterator2, $(_) => expression).