min / max_horizontal PanicException for mixed types

[cmdlineluser]

Checks

• I have checked that this issue has not already been reported.
• I have confirmed this bug exists on the latest version of Polars.

Reproducible example

import polars as pl

df = pl.DataFrame({"x": [1, 2], "y": ["three", "four"]})

df.select(pl.min_horizontal("x", "y"))
# PanicException: not implemented for dtype String

Log output

␤

Issue description

If the String column is last the expected error is raised.

df.select(pl.min_horizontal("y", "x"))
# ComputeError: cannot compare string with numeric type (i64)

Expected behavior

ComputeError

Installed versions

--------Version info---------
Polars:              1.25.2
Index type:          UInt32
Platform:            macOS-13.6.1-arm64-arm-64bit-Mach-O
Python:              3.13.0 (main, Oct  7 2024, 05:02:14) [Clang 15.0.0 (clang-1500.1.0.2.5)]
LTS CPU:             False

----Optional dependencies----
adbc_driver_manager  <not installed>
altair               <not installed>
boto3                <not installed>
cloudpickle          <not installed>
connectorx           <not installed>
deltalake            <not installed>
fastexcel            0.12.0
fsspec               <not installed>
gevent               <not installed>
google.auth          <not installed>
great_tables         0.14.0
matplotlib           <not installed>
nest_asyncio         <not installed>
numpy                2.1.3
openpyxl             3.1.5
pandas               2.2.3
pyarrow              18.0.0
pydantic             <not installed>
pyiceberg            <not installed>
sqlalchemy           <not installed>
torch                <not installed>
xlsx2csv             <not installed>
xlsxwriter           3.2.0

[kdn36]

Easily reproducible in Rust. This looks straightforward to fix in the code, and I would like to give it a try.

Code snippet

    let df = df!(
        "x" => [1, 2],
        "y" => ["three", "four"])
    .unwrap();

    let result = df.select(["x", "y"])?.min_horizontal();
    println!("result: {:?}", result);
    Ok(())

gives

thread 'main' panicked at /root/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/polars-ops-0.46.0/src/series/ops/horizontal.rs:107:17:
not implemented for dtype String
stack backtrace:
   0: rust_begin_unwind
             at /rustc/4d91de4e48198da2e33413efdcd9cd2cc0c46688/library/std/src/panicking.rs:692:5
   1: core::panicking::panic_fmt
             at /rustc/4d91de4e48198da2e33413efdcd9cd2cc0c46688/library/core/src/panicking.rs:75:14
   2: polars_ops::series::ops::horizontal::min_max_binary_columns
             at /root/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/polars-ops-0.46.0/src/series/ops/horizontal.rs:107:17
   3: polars_ops::series::ops::horizontal::min_horizontal::{{closure}}
             at /root/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/polars-ops-0.46.0/src/series/ops/horizontal.rs:170:45
   4: polars_ops::series::ops::horizontal::min_horizontal
             at /root/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/polars-ops-0.46.0/src/series/ops/horizontal.rs:175:14
   5: <polars_core::frame::DataFrame as polars_ops::series::ops::horizontal::MinMaxHorizontal>::min_horizontal
             at /root/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/polars-ops-0.46.0/src/series/ops/horizontal.rs:34:9
   6: issue_21835::main
             at ./src/main.rs:12:18
   7: core::ops::function::FnOnce::call_once
             at /root/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5