4 files changed, 44 insertions, 3 deletions
diff --git a/src/mbgl/style/expression/compound_expression.cpp b/src/mbgl/style/expression/compound_expression.cpp
index 34f0f5dea3..c637856ad9 100644
--- a/src/mbgl/style/expression/compound_expression.cpp
+++ b/src/mbgl/style/expression/compound_expression.cpp
@@ -368,6 +368,18 @@ const auto& lineProgressCompoundExpression() {
     return signature;
 }
 
+const auto& accumulatedCompoundExpression() {
+    const static auto signature = detail::makeSignature("accumulated", [](const EvaluationContext& params) -> Result<Value> {
+        if (!params.accumulated) {
+            return EvaluationError {
+                "The 'accumulated' expression is unavailable in the current evaluation context."
+            };
+        }
+        return Value(toExpressionValue(*params.accumulated));
+    });
+    return signature;
+}
+    
 const auto& hasContextCompoundExpression() {
     static auto signature = detail::makeSignature("has", [](const EvaluationContext& params, const std::string& key) -> Result<bool> {
         if (!params.feature) {
@@ -871,6 +883,7 @@ MAPBOX_ETERNAL_CONSTEXPR const auto compoundExpressionRegistry = mapbox::eternal
     { "zoom", zoomCompoundExpression },
     { "heatmap-density", heatmapDensityCompoundExpression },
     { "line-progress", lineProgressCompoundExpression },
+    { "accumulated", accumulatedCompoundExpression },
     { "has", hasContextCompoundExpression },
     { "has", hasObjectCompoundExpression },
     { "get", getContextCompoundExpression },
diff --git a/src/mbgl/style/expression/dsl.cpp b/src/mbgl/style/expression/dsl.cpp
index 70442de968..fac7dfbbd9 100644
--- a/src/mbgl/style/expression/dsl.cpp
+++ b/src/mbgl/style/expression/dsl.cpp
@@ -10,6 +10,10 @@
 #include <mbgl/style/expression/compound_expression.hpp>
 #include <mbgl/style/expression/format_expression.hpp>
 
+#include <mapbox/geojsonvt.hpp>
+#include <mbgl/style/conversion/json.hpp>
+#include <rapidjson/document.h>
+
 namespace mbgl {
 namespace style {
 namespace expression {
@@ -21,6 +25,25 @@ std::unique_ptr<Expression> compound(const char* op, std::vector<std::unique_ptr
     assert(result);
     return std::move(*result);
 }
+    
+std::unique_ptr<Expression> createExpression(const char* expr) {
+    using JSValue = rapidjson::GenericValue<rapidjson::UTF8<>, rapidjson::CrtAllocator>;
+    rapidjson::GenericDocument<rapidjson::UTF8<>, rapidjson::CrtAllocator> document;
+    document.Parse<0>(expr);
+    if (document.HasParseError()) return nullptr;
+
+    const JSValue* expression = &document;
+    expression::ParsingContext ctx;
+    expression::ParseResult parsed =
+    ctx.parseExpression(mbgl::style::conversion::Convertible(expression));
+    return parsed ? std::move(*parsed) : nullptr;
+}
+
+std::unique_ptr<Expression> createExpression(const mbgl::style::conversion::Convertible& expr) {
+    expression::ParsingContext ctx;
+    expression::ParseResult parsed = ctx.parseExpression(expr);
+    return parsed ? std::move(*parsed) : nullptr;
+}
 
 std::unique_ptr<Expression> error(std::string message) {
     return std::make_unique<Error>(std::move(message));
diff --git a/src/mbgl/style/expression/expression.cpp b/src/mbgl/style/expression/expression.cpp
index d61f435eec..6bfda99064 100644
--- a/src/mbgl/style/expression/expression.cpp
+++ b/src/mbgl/style/expression/expression.cpp
@@ -25,13 +25,17 @@ public:
         return optional<mbgl::Value>();
     }
 };
-
-
+      
 EvaluationResult Expression::evaluate(optional<float> zoom, const Feature& feature, optional<double> colorRampParameter) const {
     GeoJSONFeature f(feature);
     return this->evaluate(EvaluationContext(zoom, &f, colorRampParameter));
 }
 
+EvaluationResult Expression::evaluate(optional<mbgl::Value> accumulated, const Feature& feature) const {
+    GeoJSONFeature f(feature);
+    return this->evaluate(EvaluationContext(accumulated, &f));
+}
+
 } // namespace expression
 } // namespace style
 } // namespace mbgl
diff --git a/src/mbgl/style/expression/parsing_context.cpp b/src/mbgl/style/expression/parsing_context.cpp
index a7c04f563d..6ce3a9bfaa 100644
--- a/src/mbgl/style/expression/parsing_context.cpp
+++ b/src/mbgl/style/expression/parsing_context.cpp
@@ -73,7 +73,8 @@ bool isConstant(const Expression& expression) {
     
     return isFeatureConstant(expression) &&
         isGlobalPropertyConstant(expression, std::array<std::string, 2>{{"zoom", "heatmap-density"}}) &&
-        isGlobalPropertyConstant(expression, std::array<std::string, 2>{{"zoom", "line-progress"}});
+        isGlobalPropertyConstant(expression, std::array<std::string, 2>{{"zoom", "line-progress"}}) &&
+        isGlobalPropertyConstant(expression, std::array<std::string, 2>{{"zoom", "accumulated"}});
 }
 
 using namespace mbgl::style::conversion;