Module DA.List.BuiltinOrder¶
Note: This is only supported in DAMLLF 1.11 or later.
This module provides variants of other standard library
functions that are based on the builtin DamlLF ordering rather
than userdefined ordering. This is the same order also used
by DA.Map
.
These functions are usually much more efficient than their
Ord
based counterparts.
Note that the functions in this module still require Ord
constraints. This is purely to enforce that you don’t
pass in values that cannot be compared, e.g., functions. The
implementation of those instances is not used.
Functions¶
 dedup
: Ord a => [a] > [a]
dedup l
removes duplicate elements from a list. In particular, it keeps only the first occurrence of each element.dedup
is stable so the elements in the output are ordered by their first occurrence in the input. If you do not need stability, consider usingdedupSort
which is more efficient.>>> dedup [3, 1, 1, 3] [3, 1]
 dedupOn
: Ord k => (v > k) > [v] > [v]
A version of
dedup
where deduplication is done after applying the given function. Example use:dedupOn (.employeeNo) employees
.dedupOn
is stable so the elements in the output are ordered by their first occurrence in the input. If you do not need stability, consider usingdedupOnSort
which is more efficient.>>> dedupOn fst [(3, "a"), (1, "b"), (1, "c"), (3, "d")] [(3, "a"), (1, "b")]
 dedupSort
: Ord a => [a] > [a]
dedupSort
is a more efficient variant ofdedup
that does not preserve the order of the input elements. Instead the output will be sorted acoording to the builtin DamlLF ordering.>>> dedupSort [3, 1, 1, 3] [1, 3]
 dedupOnSort
: Ord k => (v > k) > [v] > [v]
dedupOnSort
is a more efficient variant ofdedupOn
that does not preserve the order of the input elements. Instead the output will be sorted on the values returned by the function.For duplicates, the first element in the list will be included in the output.
>>> dedupOnSort fst [(3, "a"), (1, "b"), (1, "c"), (3, "d")] [(1, "b"), (3, "a")]
 sort
: Ord a => [a] > [a]
Sort the list according to the DamlLF ordering.
Values that are identical according to the builtin DamlLF ordering are indistinguishable so stability is not relevant here.
>>> sort [3,1,2] [1,2,3]
 sortOn
: Ord b => (a > b) > [a] > [a]
sortOn f
is a version of sort that allows sorting on the result of the given function.sortOn
is stable so elements that map to the same sort key will be ordered by their position in the input.>>> sortOn fst [(3, "a"), (1, "b"), (3, "c"), (2, "d")] [(1, "b"), (2, "d"), (3, "a"), (3, "c")]
 unique

Returns True if and only if there are no duplicate elements in the given list.
>>> unique [1, 2, 3] True