diff --git a/include/musique.hh b/include/musique.hh
index 3a88d96..41bad3a 100644
--- a/include/musique.hh
+++ b/include/musique.hh
@@ -1099,4 +1099,9 @@ static constexpr bool is_callable(Value::Type type)
 Result<std::vector<Value>> flatten(Interpreter &i, std::span<Value>);
 Result<std::vector<Value>> flatten(Interpreter &i, std::vector<Value>);
 
+template<> struct std::hash<Token>  { std::size_t operator()(Token  const&) const; };
+template<> struct std::hash<Ast>    { std::size_t operator()(Ast    const&) const; };
+template<> struct std::hash<Number> { std::size_t operator()(Number const&) const; };
+template<> struct std::hash<Value>  { std::size_t operator()(Value  const&) const; };
+
 #endif
diff --git a/include/musique_internal.hh b/include/musique_internal.hh
index 52679c5..f6234cf 100644
--- a/include/musique_internal.hh
+++ b/include/musique_internal.hh
@@ -97,4 +97,7 @@ struct Interpreter::Incoming_Midi_Callbacks
 enum class Midi_Connection_Type { Output, Input };
 Result<void> ensure_midi_connection_available(Interpreter&, Midi_Connection_Type, std::string_view operation_name);
 
+constexpr std::size_t hash_combine(std::size_t lhs, std::size_t rhs) {
+	return lhs ^= rhs + 0x9e3779b9 + (lhs << 6) + (lhs >> 2);
+}
 #endif
diff --git a/src/builtin_functions.cc b/src/builtin_functions.cc
index 4e62e9d..7c64472 100644
--- a/src/builtin_functions.cc
+++ b/src/builtin_functions.cc
@@ -4,6 +4,7 @@
 #include <random>
 #include <memory>
 #include <iostream>
+#include <unordered_set>
 
 void Interpreter::register_callbacks()
 {
@@ -601,6 +602,48 @@ static Result<Value> builtin_rotate(Interpreter &i, std::vector<Value> args)
 	return Value::from(std::move(array));
 }
 
+/// Returns unique collection of arguments
+static Result<Value> builtin_unique(Interpreter &i, std::vector<Value> args)
+{
+	auto array = Try(flatten(i, args));
+	std::unordered_set<Value> seen;
+
+	std::vector<Value> result;
+	for (auto &el : array) {
+		if (!seen.contains(el)) {
+			seen.insert(el);
+			result.push_back(std::move(el));
+		}
+	}
+	return Value::from(std::move(result));
+}
+
+/// Returns arguments with all successive copies eliminated
+static Result<Value> builtin_uniq(Interpreter &i, std::vector<Value> args)
+{
+	auto array = Try(flatten(i, args));
+
+	std::optional<Value> previous;
+	std::vector<Value> result;
+
+	for (auto &el : array) {
+		if (previous && *previous == el)
+			continue;
+		result.push_back(el);
+		previous = std::move(el);
+	}
+	return Value::from(std::move(result));
+}
+
+static Result<Value> builtin_hash(Interpreter&, std::vector<Value> args)
+{
+	return Value::from(Number(
+		std::accumulate(args.cbegin(), args.cend(), size_t(0), [](size_t h, Value const& v) {
+			return hash_combine(h, std::hash<Value>{}(v));
+		})
+	));
+}
+
 /// Build chord from arguments
 static Result<Value> builtin_chord(Interpreter &i, std::vector<Value> args)
 {
@@ -714,6 +757,7 @@ void Interpreter::register_builtin_functions()
 	global.force_define("flat",           builtin_flat);
 	global.force_define("floor",          apply_numeric_transform<&Number::floor>);
 	global.force_define("for",            builtin_for);
+	global.force_define("hash",           builtin_hash);
 	global.force_define("if",             builtin_if);
 	global.force_define("incoming",       builtin_incoming);
 	global.force_define("instrument",     builtin_program_change);
@@ -738,6 +782,8 @@ void Interpreter::register_builtin_functions()
 	global.force_define("sort",           builtin_sort);
 	global.force_define("try",            builtin_try);
 	global.force_define("typeof",         builtin_typeof);
+	global.force_define("uniq",           builtin_uniq);
+	global.force_define("unique",         builtin_unique);
 	global.force_define("up",             builtin_range<Range_Direction::Up>);
 	global.force_define("update",         builtin_update);
 }
diff --git a/src/lexer.cc b/src/lexer.cc
index 6ed9dfa..5bd30c2 100644
--- a/src/lexer.cc
+++ b/src/lexer.cc
@@ -1,4 +1,5 @@
 #include <musique.hh>
+#include <musique_internal.hh>
 
 #include <iomanip>
 
@@ -277,3 +278,9 @@ std::string_view type_name(Token::Type type)
 	}
 	unreachable();
 }
+
+std::size_t std::hash<Token>::operator()(Token const& token) const
+{
+	return hash_combine(std::hash<std::string_view>{}(token.source), size_t(token.type));
+}
+
diff --git a/src/number.cc b/src/number.cc
index b6291c3..cef8565 100644
--- a/src/number.cc
+++ b/src/number.cc
@@ -1,4 +1,6 @@
 #include <musique.hh>
+#include <musique_internal.hh>
+
 #include <cmath>
 #include <numeric>
 #include <charconv>
@@ -332,3 +334,9 @@ Result<Number> Number::pow(Number n) const
 	// We need to protect ourselfs against even roots of negative numbers.
 	unimplemented();
 }
+
+std::size_t std::hash<Number>::operator()(Number const& value) const
+{
+	std::hash<Number::value_type> h;
+	return hash_combine(h(value.num), h(value.den));
+}
diff --git a/src/parser.cc b/src/parser.cc
index a7fa2af..1cbf874 100644
--- a/src/parser.cc
+++ b/src/parser.cc
@@ -1,5 +1,8 @@
 #include <musique.hh>
+#include <musique_internal.hh>
+
 #include <iostream>
+#include <numeric>
 
 static Ast wrap_if_several(std::vector<Ast> &&ast, Ast(*wrapper)(std::vector<Ast>));
 
@@ -616,3 +619,12 @@ void dump(Ast const& tree, unsigned indent)
 		std::cout << std::flush;
 	}
 }
+
+std::size_t std::hash<Ast>::operator()(Ast const& value) const
+{
+	auto h = std::hash<Token>{}(value.token);
+	h = std::accumulate(value.arguments.begin(), value.arguments.end(), h, [this](size_t h, Ast const& node) {
+		return hash_combine(h, operator()(node));
+	});
+	return hash_combine(size_t(value.type), h);
+}
diff --git a/src/value.cc b/src/value.cc
index a871acb..b2506e7 100644
--- a/src/value.cc
+++ b/src/value.cc
@@ -1,4 +1,7 @@
 #include <musique.hh>
+#include <musique_internal.hh>
+
+#include <numeric>
 
 /// Finds numeric value of note. This form is later used as in
 /// note to midi resolution in formula octave * 12 + note_index
@@ -522,3 +525,31 @@ Result<std::vector<Value>> flatten(Interpreter &i, std::vector<Value> args)
 {
 	return flatten(i, std::span(args));
 }
+
+std::size_t std::hash<Value>::operator()(Value const& value) const
+{
+	size_t value_hash = 0;
+	switch (value.type) {
+	break; case Value::Type::Nil:       value_hash = 0;
+	break; case Value::Type::Number:    value_hash = std::hash<Number>{}(value.n);
+	break; case Value::Type::Symbol:    value_hash = std::hash<std::string>{}(value.s);
+	break; case Value::Type::Bool:      value_hash = std::hash<bool>{}(value.b);
+	break; case Value::Type::Intrinsic: value_hash = ptrdiff_t(value.intr);
+	break; case Value::Type::Block:     value_hash = hash_combine(std::hash<Ast>{}(value.blk.body), value.blk.parameters.size());
+
+	break; case Value::Type::Array:
+		value_hash = std::accumulate(value.array.elements.begin(), value.array.elements.end(), value_hash, [this](size_t h, Value const& v) {
+			return hash_combine(h, operator()(v));
+		});
+
+	break; case Value::Type::Music:
+		value_hash = std::accumulate(value.chord.notes.begin(), value.chord.notes.end(), value_hash, [](size_t h, Note const& n) {
+			h = hash_combine(h, n.base);
+			h = hash_combine(h, std::hash<std::optional<Number>>{}(n.length));
+			h = hash_combine(h, std::hash<std::optional<i8>>{}(n.octave));
+			return h;
+		});
+	}
+
+	return hash_combine(value_hash, size_t(value.type));
+}