[GitHub] [arrow] nealrichardson commented on a change in pull request #8894: ARROW-10322: [C++][Dataset] Minimize Expression

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nealrichardson commented on a change in pull request #8894:
URL: https://github.com/apache/arrow/pull/8894#discussion_r541147763



##########
File path: r/src/expression.cpp
##########
@@ -19,93 +19,98 @@
 
 #if defined(ARROW_R_WITH_ARROW)
 
+#include <arrow/compute/api_scalar.h>
 #include <arrow/dataset/api.h>
 namespace ds = ::arrow::dataset;
 
+std::shared_ptr<ds::Expression> Share(ds::Expression expr) {
+  return std::make_shared<ds::Expression>(std::move(expr));
+}
+

Review comment:
       Would it be appropriate in this PR to add the `compute::CallFunction` equivalent for dataset expressions? Before I can add any new expressions, we'll need it. 
   
   I'm guessing it looks like:
   
   ```
   std::shared_ptr<ds::Expression> dataset___expr(std::string func_name, cpp11::list args, cpp11::list options)
   ```
   
   and calls `ds::call()` inside it?




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