Merge pull request #83 from pola-rs/fix-lazy-dtype-arg-previous-greater

fix lazy dtype in arg_previous_greater

Author: MarcoGorelli

Cargo.lock

@@ -1,5 +1,6 @@
 use polars::prelude::*;
 
+
 pub(crate) fn impl_arg_previous_greater<T>(ca: &ChunkedArray<T>) -> IdxCa
 where
     T: PolarsNumericType,

src/arg_previous_greater.rs

@@ -83,8 +83,16 @@ fn to_julian_date(inputs: &[Series]) -> PolarsResult<Series> {
     impl_to_julian_date(s)
 }
 
-// todo: can we make this bigidx-dependent?
-#[polars_expr(output_type=UInt32)]
+
+fn list_idx_dtype(input_fields: &[Field]) -> PolarsResult<Field> {
+    let field = Field::new(
+        input_fields[0].name.clone(),
+        DataType::List(Box::new(IDX_DTYPE))
+    );
+    Ok(field.clone())
+}
+
+#[polars_expr(output_type_func=list_idx_dtype)]
 fn arg_previous_greater(inputs: &[Series]) -> PolarsResult<Series> {
     let ser = &inputs[0];
     match ser.dtype() {