diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer.res
index c9c9f41e..24c985d8 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer.res
@@ -11,4 +11,5 @@ type expressionValue = ReducerInterface_ExpressionValue.expressionValue
 type externalBindings = ReducerInterface_ExpressionValue.externalBindings
 let evaluate = Expression.evaluate
 let evaluateUsingOptions = Expression.evaluateUsingOptions
+let evaluatePartialUsingExternalBindings = Expression.evaluatePartialUsingExternalBindings
 let parse = Expression.parse
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer.resi b/packages/squiggle-lang/src/rescript/Reducer/Reducer.resi
index 880dd1e7..4e86361a 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer.resi
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer.resi
@@ -21,6 +21,12 @@ let evaluateUsingOptions: (
   string,
 ) => result<expressionValue, errorValue>
 @genType
+let evaluatePartialUsingExternalBindings: (
+  string,
+  QuriSquiggleLang.ReducerInterface_ExpressionValue.externalBindings,
+  QuriSquiggleLang.ReducerInterface_ExpressionValue.environment,
+) => result<externalBindings, errorValue>
+@genType
 let evaluate: string => result<expressionValue, errorValue>
 
 let parse: string => result<Expression.expression, errorValue>
diff --git a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res
index bbd7cc3b..02043320 100644
--- a/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res
+++ b/packages/squiggle-lang/src/rescript/Reducer/Reducer_Expression/Reducer_Expression.res
@@ -114,3 +114,15 @@ let evaluate = (code: string): result<expressionValue, errorValue> => {
   evaluateUsingOptions(~environment=None, ~externalBindings=None, code)
 }
 let eval = evaluate
+let evaluatePartialUsingExternalBindings = (
+  code: string,
+  externalBindings: ReducerInterface_ExpressionValue.externalBindings,
+  environment: ReducerInterface_ExpressionValue.environment,
+): result<externalBindings, errorValue> => {
+  let rAnswer = evaluateUsingOptions(~environment=Some(environment), ~externalBindings=Some(externalBindings), code)
+  switch rAnswer {
+    | Ok(EvRecord(externalBindings)) => Ok(externalBindings)
+    | Ok(_) => Error(Reducer_ErrorValue.RESyntaxError(`Partials must end with an assignment or record`))
+    | Error(err) => err->Error
+  }
+}