1 files changed, 29 insertions, 0 deletions
diff --git a/src/mbgl/style/expression/is_expression.cpp b/src/mbgl/style/expression/is_expression.cpp
new file mode 100644
index 0000000000..77212f6a1e
--- /dev/null
+++ b/src/mbgl/style/expression/is_expression.cpp
@@ -0,0 +1,29 @@
+#include <mbgl/style/expression/is_expression.hpp>
+#include <mbgl/style/expression/compound_expression.hpp>
+#include <mbgl/style/expression/parsing_context.hpp>
+
+#include <mbgl/style/conversion.hpp>
+
+#include <unordered_set>
+
+namespace mbgl {
+namespace style {
+namespace expression {
+
+using namespace mbgl::style::conversion;
+
+bool isExpression(const Convertible& value) {
+    const ExpressionRegistry& registry = getExpressionRegistry();
+
+    if (!isArray(value) || arrayLength(value) == 0) return false;
+    optional<std::string> name = toString(arrayMember(value, 0));
+    if (!name) return false;
+    
+    return (registry.find(*name) != registry.end()) ||
+        (CompoundExpressionRegistry::definitions.find(*name) != CompoundExpressionRegistry::definitions.end());
+}
+
+
+} // namespace expression
+} // namespace style
+} // namespace mbgl