rhai/examples/strings.rs

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///! This example registers a variety of functions that operate on strings.
///! Remember to use `ImmutableString` or `&str` instead of `String` as parameters.
use rhai::{Engine, EvalAltResult, ImmutableString, Scope, INT};
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use std::io::{stdin, stdout, Write};
/// Trim whitespace from a string. The original string argument is changed.
///
/// This version uses `&mut ImmutableString`
fn trim_string(s: &mut ImmutableString) {
*s = s.trim().into();
}
/// Notice this is different from the built-in Rhai 'len' function for strings
/// which counts the actual number of Unicode _characters_ in a string.
/// This version simply counts the number of _bytes_ in the UTF-8 representation.
///
/// This version uses `&str`.
fn count_string_bytes(s: &str) -> INT {
s.len() as INT
}
/// This version uses `ImmutableString` and `&str`.
fn find_substring(s: ImmutableString, sub: &str) -> INT {
s.as_str().find(sub).map(|x| x as INT).unwrap_or(-1)
}
fn main() -> Result<(), Box<EvalAltResult>> {
// Create a `raw` Engine with no built-in string functions.
let mut engine = Engine::new_raw();
// Register string functions
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engine
.register_fn("trim", trim_string)
.register_fn("len", count_string_bytes)
.register_fn("index_of", find_substring)
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// Register string functions using closures
.register_fn("display", |label: &str, value: INT| {
println!("{}: {}", label, value)
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})
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.register_fn("display", |label: ImmutableString, value: &str| {
println!(r#"{}: "{}""#, label, value) // Quote the input string
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});
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let mut scope = Scope::new();
let mut input = String::new();
loop {
scope.clear();
println!("Type something. Press Ctrl-C to exit.");
print!("strings> ");
stdout().flush().expect("couldn't flush stdout");
input.clear();
if let Err(err) = stdin().read_line(&mut input) {
panic!("input error: {}", err);
}
scope.push("x", input.clone());
println!("Line: {}", input.replace('\r', "\\r").replace('\n', "\\n"));
engine.consume_with_scope(
&mut scope,
r#"
display("Length", x.len());
x.trim();
display("Trimmed", x);
display("Trimmed Length", x.len());
display("Index of \"!!!\"", x.index_of("!!!"));
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"#,
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)?;
println!();
}
}