01.rs

use polars_core::error::PolarsResult;
use polars_core::prelude::*;
use polars_plan::plans::FieldsMapper;
use pyo3_polars_derive::polars_expr;

fn horizontal_product_output(input_fields: &[Field]) -> PolarsResult<Field> {
    FieldsMapper::new(input_fields).map_to_supertype()
}

#[polars_expr(output_type_func=horizontal_product_output)]
fn horizontal_product(series: &[Series], kwargs: Option<&str>) -> PolarsResult<Series> {
    let _ = kwargs;

    let mut acc = series[0].clone();
    for s in &series[1..] {
        acc = (&acc * s)?
    }
    Ok(acc)
}

fn main() {}