1 files changed, 72 insertions, 0 deletions
diff --git a/include/mbgl/style/expression/let.hpp b/include/mbgl/style/expression/let.hpp
new file mode 100644
index 0000000000..aaa16ca0c2
--- /dev/null
+++ b/include/mbgl/style/expression/let.hpp
@@ -0,0 +1,72 @@
+#pragma once
+
+#include <mbgl/style/expression/expression.hpp>
+#include <mbgl/style/expression/parsing_context.hpp>
+#include <mbgl/style/conversion.hpp>
+
+#include <memory>
+#include <map>
+
+namespace mbgl {
+namespace style {
+namespace expression {
+
+class Let : public Expression {
+public:
+    using Bindings = std::map<std::string, std::shared_ptr<Expression>>;
+    
+    Let(Bindings bindings_, std::unique_ptr<Expression> result_) :
+        Expression(result_->getType()),
+        bindings(std::move(bindings_)),
+        result(std::move(result_))
+    {}
+    
+    static ParseResult parse(const mbgl::style::conversion::Convertible&, ParsingContext&);
+    
+    EvaluationResult evaluate(const EvaluationContext& params) const override;
+    void eachChild(const std::function<void(const Expression&)>&) const override;
+
+    bool operator==(const Expression& e) const override {
+        if (auto rhs = dynamic_cast<const Let*>(&e)) {
+            return *result == *(rhs->result);
+        }
+        return false;
+    }
+
+    Expression* getResult() const {
+        return result.get();
+    }
+
+private:
+    Bindings bindings;
+    std::unique_ptr<Expression> result;
+};
+
+class Var : public Expression {
+public:
+    Var(std::string name_, std::shared_ptr<Expression> value_) :
+        Expression(value_->getType()),
+        name(std::move(name_)),
+        value(value_)
+    {}
+
+    static ParseResult parse(const mbgl::style::conversion::Convertible&, ParsingContext&);
+
+    EvaluationResult evaluate(const EvaluationContext& params) const override;
+    void eachChild(const std::function<void(const Expression&)>&) const override;
+
+    bool operator==(const Expression& e) const override {
+        if (auto rhs = dynamic_cast<const Var*>(&e)) {
+            return *value == *(rhs->value);
+        }
+        return false;
+    }
+    
+private:
+    std::string name;
+    std::shared_ptr<Expression> value;
+};
+
+} // namespace expression
+} // namespace style
+} // namespace mbgl