diff options
Diffstat (limited to 'third_party/bazel/rules_haskell/haskell/private/list.bzl')
-rw-r--r-- | third_party/bazel/rules_haskell/haskell/private/list.bzl | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/third_party/bazel/rules_haskell/haskell/private/list.bzl b/third_party/bazel/rules_haskell/haskell/private/list.bzl new file mode 100644 index 000000000000..14ffd5f06876 --- /dev/null +++ b/third_party/bazel/rules_haskell/haskell/private/list.bzl @@ -0,0 +1,26 @@ +"""Helper functions on lists.""" + +load(":private/set.bzl", "set") + +def _dedup_on(f, list_): + """deduplicate `list_` by comparing the result of applying + f to each element (e.g. comparing sub fields) + + def compare_x(el): + return el.x + + dedup_on([struct(x=3), struct(x=4), struct(x=3)], compare_x) + => [struct(x=3), struct(x=4)] + """ + seen = set.empty() + deduped = [] + for el in list_: + by = f(el) + if not set.is_member(seen, by): + set.mutable_insert(seen, by) + deduped.append(el) + return deduped + +list = struct( + dedup_on = _dedup_on, +) |