Implement Serialize and Deserialize

Cargo.toml

@@ -12,8 +12,9 @@ edition = "2021"
 
 [dependencies]
 num-traits = "0.2"
+serde = { version = "1.0.188", optional = true}
 
 [dev-dependencies]
 maplit = "1.0"
 rand = "0.8.5"
-
+serde_json = "1.0.107"

README.md

@@ -15,6 +15,10 @@ union, etc. are of course still supported.
 
 [multiset]: https://en.wikipedia.org/wiki/Set_(abstract_data_type)#Multiset
 
+## Cargo Features
+
+- `serde` implements `serde::Serialize` and `serde::Deserialize` for `Counter`.
+
 ## Examples
 
 ### Just count an iterable

src/impls.rs

@@ -7,6 +7,8 @@ mod from_iterator;
 mod index;
 mod intersection;
 mod into_iterator;
+#[cfg(feature = "serde")]
+mod serialize;
 mod sub_iterable;
 mod sub_self;
 mod union;

src/impls/serialize.rs

@@ -0,0 +1,32 @@
+use crate::Counter;
+
+use std::hash::Hash;
+use num_traits::Zero;
+use serde::{Serialize, Deserialize};
+use serde::ser::Serializer;
+use serde::de::Deserializer;
+
+
+impl<T, N> Serialize for Counter<T, N> 
+where
+    T: Serialize + Hash + Eq,
+    N: Serialize,
+{
+    fn serialize<S>(&self, serializer:S) -> Result<S::Ok, S::Error>
+    where S: Serializer {
+        self.map.serialize(serializer)
+    }
+}
+
+impl<'de, T, N> Deserialize<'de> for Counter<T, N>
+where
+    T: Deserialize<'de> + Hash + Eq,
+    N: Deserialize<'de> + Zero,
+{
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where D: Deserializer<'de> {
+        let map = <_>::deserialize(deserializer)?;
+        let zero = N::zero();
+        Ok(Counter { map, zero })
+    }
+}

tests/tests.rs

@@ -185,4 +185,13 @@ mod tests {
         a[&'e'] = -2;
         assert!(a.is_subset(&b));
     }
+
+    #[cfg(feature = "serde")]
+    #[test]
+    fn test_serialize_deserialize() {
+        let a = "abbccc".chars().collect::<Counter<_>>();
+        let serialized = serde_json::to_string(&a).unwrap();
+        let b: Counter<char> = serde_json::from_str(&serialized).unwrap();
+        assert!(a == b)
+    }
 }