risingwave_expr_impl/scalar/
lower.rs

1// Copyright 2025 RisingWave Labs
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15use std::fmt::Write;
16
17use risingwave_expr::function;
18
19#[function("lower(varchar) -> varchar")]
20pub fn lower(s: &str, writer: &mut impl Write) {
21    for c in s.chars() {
22        writer.write_char(c.to_ascii_lowercase()).unwrap();
23    }
24}
25
26#[cfg(test)]
27mod tests {
28    use super::*;
29
30    #[test]
31    fn test_lower() {
32        let cases = [
33            ("HELLO WORLD", "hello world"),
34            ("hello RUST", "hello rust"),
35            ("3 PINEAPPLES", "3 pineapples"),
36        ];
37
38        for (s, expected) in cases {
39            let mut writer = String::new();
40            lower(s, &mut writer);
41            assert_eq!(writer, expected);
42        }
43    }
44}
risingwave_expr_impl/scalar/lower.rs

risingwave_expr_impl/scalar/
lower.rs
