bringing docs up to date

notes/FunStuff.txt

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+Content-Type: text/x-zim-wiki
+Wiki-Format: zim 0.4
+Creation-Date: 2020-02-12T21:45:56-08:00
+
+====== FunStuff ======
+
+===== Dynamic Hash Map Keys =====
+{{{code: lang="rust" linenumbers="True"
+pub mod dynhash {
+	use std::any::Any;
+	use std::hash::{Hash, Hasher};
+
+	pub trait DynEq: Any {
+		fn dyn_eq(&self, other: &dyn DynEq) -> bool;
+
+		fn as_any(&self) -> &dyn Any;
+	}
+
+	pub trait DynHash: DynEq {
+		fn dyn_hash(&self, hasher: &mut dyn Hasher);
+
+		fn as_dyn_eq(&self) -> &dyn DynEq;
+	}
+
+	impl<H: Eq + Any> DynEq for H {
+		fn dyn_eq(&self, other: &dyn DynEq) -> bool {
+			if let Some(other) = other.as_any().downcast_ref::<H>() {
+				self == other
+			} else {
+				false
+			}
+		}
+
+		fn as_any(&self) -> &dyn Any {
+			self
+		}
+	}
+
+	impl<H: Hash + DynEq> DynHash for H {
+		fn dyn_hash(&self, mut hasher: &mut dyn Hasher) {
+			H::hash(self, &mut hasher)
+		}
+
+		fn as_dyn_eq(&self) -> &dyn DynEq {
+			self
+		}
+	}
+
+	impl PartialEq for dyn DynHash {
+		fn eq(&self, other: &dyn DynHash) -> bool {
+			self.dyn_eq(other.as_dyn_eq())
+		}
+	}
+
+	impl Eq for dyn DynHash {}
+
+	impl Hash for dyn DynHash {
+		fn hash<H: Hasher>(&self, hasher: &mut H) {
+			self.dyn_hash(hasher)
+		}
+	}
+}
+}}}