71 lines
1.3 KiB
Plaintext
71 lines
1.3 KiB
Plaintext
pub opaque type AssocList<key, value> {
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inner: List<(key, value)>,
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}
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pub fn new() -> AssocList<key, value> {
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AssocList { inner: [] }
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}
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pub fn from_list(xs: List<(key, value)>) -> AssocList<key, value> {
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AssocList { inner: do_from_list(xs) }
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}
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fn do_from_list(xs: List<(key, value)>) -> List<(key, value)> {
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when xs is {
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[] ->
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[]
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[(k, v), ..rest] ->
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do_insert(do_from_list(rest), k, v)
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}
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}
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pub fn insert(
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in m: AssocList<key, value>,
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key k: key,
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value v: value,
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) -> AssocList<key, value> {
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AssocList { inner: do_insert(m.inner, k, v) }
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}
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fn do_insert(elems: List<(key, value)>, k: key, v: value) -> List<(key, value)> {
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when elems is {
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[] ->
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[(k, v)]
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[(k2, v2), ..rest] ->
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if k == k2 {
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[(k, v), ..rest]
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} else {
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[(k2, v2), ..do_insert(rest, k, v)]
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}
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}
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}
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pub fn union(
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left: AssocList<key, value>,
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right: AssocList<key, value>,
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) -> AssocList<key, value> {
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AssocList { inner: do_union(left.inner, right.inner) }
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}
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fn do_union(
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left: List<(key, value)>,
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right: List<(key, value)>,
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) -> List<(key, value)> {
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when left is {
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[] ->
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right
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[(k, v), ..rest] ->
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do_union(rest, do_insert(right, k, v))
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}
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}
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fn fixture_1() {
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new()
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|> insert("foo", 42)
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|> insert("bar", 14)
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}
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test union_1() {
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union(fixture_1(), new()) == fixture_1()
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}
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