266 lines
8.4 KiB
Rust
266 lines
8.4 KiB
Rust
//! Module that defines public event handlers for [`Engine`].
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use crate::engine::EvalContext;
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use crate::func::SendSync;
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use crate::{Dynamic, Engine, EvalAltResult, Position};
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#[cfg(feature = "no_std")]
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use std::prelude::v1::*;
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impl Engine {
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/// Provide a callback that will be invoked before each variable access.
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///
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/// # Callback Function Signature
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///
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/// The callback function signature takes the following form:
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///
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/// > `Fn(name: &str, index: usize, context: &EvalContext)`
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/// > ` -> Result<Option<Dynamic>, Box<EvalAltResult>> + 'static`
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///
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/// where:
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/// * `index`: an offset from the bottom of the current [`Scope`][crate::Scope] that the
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/// variable is supposed to reside. Offsets start from 1, with 1 meaning the last variable in
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/// the current [`Scope`][crate::Scope]. Essentially the correct variable is at position
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/// `scope.len() - index`. If `index` is zero, then there is no pre-calculated offset position
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/// and a search through the current [`Scope`][crate::Scope] must be performed.
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///
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/// * `context`: the current [evaluation context][`EvalContext`].
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///
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/// ## Return value
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///
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/// * `Ok(None)`: continue with normal variable access.
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/// * `Ok(Some(Dynamic))`: the variable's value.
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///
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/// ## Raising errors
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///
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/// Return `Err(...)` if there is an error.
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///
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/// # Example
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///
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/// ```
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/// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
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/// use rhai::Engine;
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///
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/// let mut engine = Engine::new();
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///
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/// // Register a variable resolver.
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/// engine.on_var(|name, _, _| {
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/// match name {
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/// "MYSTIC_NUMBER" => Ok(Some(42_i64.into())),
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/// _ => Ok(None)
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/// }
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/// });
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///
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/// engine.eval::<i64>("MYSTIC_NUMBER")?;
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///
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/// # Ok(())
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/// # }
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/// ```
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#[inline(always)]
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pub fn on_var(
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&mut self,
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callback: impl Fn(&str, usize, &EvalContext) -> Result<Option<Dynamic>, Box<EvalAltResult>>
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+ SendSync
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+ 'static,
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) -> &mut Self {
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self.resolve_var = Some(Box::new(callback));
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self
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}
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/// _(internals)_ Provide a callback that will be invoked during parsing to remap certain tokens.
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/// Exported under the `internals` feature only.
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///
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/// # Callback Function Signature
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///
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/// The callback function signature takes the following form:
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///
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/// > `Fn(token: Token, pos: Position, state: &TokenizeState) -> Token`
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///
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/// where:
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/// * [`token`][crate::tokenizer::Token]: current token parsed
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/// * [`pos`][`Position`]: location of the token
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/// * [`state`][crate::tokenizer::TokenizeState]: current state of the tokenizer
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///
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/// ## Raising errors
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///
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/// It is possible to raise a parsing error by returning
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/// [`Token::LexError`][crate::tokenizer::Token::LexError] as the mapped token.
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///
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/// # Example
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///
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/// ```
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/// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
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/// use rhai::{Engine, Token};
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///
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/// let mut engine = Engine::new();
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///
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/// // Register a token mapper.
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/// engine.on_parse_token(|token, _, _| {
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/// match token {
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/// // Convert all integer literals to strings
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/// Token::IntegerConstant(n) => Token::StringConstant(n.to_string().into()),
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/// // Convert 'begin' .. 'end' to '{' .. '}'
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/// Token::Identifier(s) if &*s == "begin" => Token::LeftBrace,
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/// Token::Identifier(s) if &*s == "end" => Token::RightBrace,
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/// // Pass through all other tokens unchanged
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/// _ => token
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/// }
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/// });
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///
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/// assert_eq!(engine.eval::<String>("42")?, "42");
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/// assert_eq!(engine.eval::<bool>("true")?, true);
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/// assert_eq!(engine.eval::<String>("let x = 42; begin let x = 0; end; x")?, "42");
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///
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/// # Ok(())
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/// # }
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/// ```
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#[cfg(feature = "internals")]
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#[inline(always)]
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pub fn on_parse_token(
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&mut self,
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callback: impl Fn(
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crate::tokenizer::Token,
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Position,
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&crate::tokenizer::TokenizeState,
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) -> crate::tokenizer::Token
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+ SendSync
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+ 'static,
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) -> &mut Self {
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self.token_mapper = Some(Box::new(callback));
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self
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}
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/// Register a callback for script evaluation progress.
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///
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/// Not available under `unchecked`.
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///
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/// # Callback Function Signature
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///
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/// The callback function signature takes the following form:
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///
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/// > `Fn(counter: u64) -> Option<Dynamic>`
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///
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/// ## Return value
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///
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/// * `None`: continue running the script.
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/// * `Some(Dynamic)`: terminate the script with the specified exception value.
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///
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/// # Example
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///
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/// ```
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/// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
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/// # use std::sync::RwLock;
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/// # use std::sync::Arc;
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/// use rhai::Engine;
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///
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/// let result = Arc::new(RwLock::new(0_u64));
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/// let logger = result.clone();
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///
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/// let mut engine = Engine::new();
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///
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/// engine.on_progress(move |ops| {
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/// if ops > 1000 {
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/// Some("Over 1,000 operations!".into())
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/// } else if ops % 123 == 0 {
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/// *logger.write().unwrap() = ops;
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/// None
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/// } else {
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/// None
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/// }
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/// });
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///
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/// engine.run("for x in 0..5000 { print(x); }")
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/// .expect_err("should error");
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///
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/// assert_eq!(*result.read().unwrap(), 984);
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///
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/// # Ok(())
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/// # }
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/// ```
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#[cfg(not(feature = "unchecked"))]
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#[inline(always)]
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pub fn on_progress(
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&mut self,
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callback: impl Fn(u64) -> Option<Dynamic> + SendSync + 'static,
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) -> &mut Self {
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self.progress = Some(Box::new(callback));
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self
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}
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/// Override default action of `print` (print to stdout using [`println!`])
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///
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/// # Example
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///
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/// ```
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/// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
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/// # use std::sync::RwLock;
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/// # use std::sync::Arc;
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/// use rhai::Engine;
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///
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/// let result = Arc::new(RwLock::new(String::new()));
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///
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/// let mut engine = Engine::new();
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///
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/// // Override action of 'print' function
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/// let logger = result.clone();
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/// engine.on_print(move |s| logger.write().unwrap().push_str(s));
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///
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/// engine.run("print(40 + 2);")?;
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///
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/// assert_eq!(*result.read().unwrap(), "42");
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/// # Ok(())
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/// # }
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/// ```
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#[inline(always)]
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pub fn on_print(&mut self, callback: impl Fn(&str) + SendSync + 'static) -> &mut Self {
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self.print = Some(Box::new(callback));
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self
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}
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/// Override default action of `debug` (print to stdout using [`println!`])
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///
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/// # Callback Function Signature
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///
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/// The callback function signature passed takes the following form:
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///
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/// > `Fn(text: &str, source: Option<&str>, pos: Position)`
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///
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/// where:
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/// * `text`: the text to display
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/// * `source`: current source, if any
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/// * [`pos`][`Position`]: location of the `debug` call
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///
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/// # Example
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///
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/// ```
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/// # fn main() -> Result<(), Box<rhai::EvalAltResult>> {
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/// # use std::sync::RwLock;
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/// # use std::sync::Arc;
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/// use rhai::Engine;
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///
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/// let result = Arc::new(RwLock::new(String::new()));
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///
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/// let mut engine = Engine::new();
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///
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/// // Override action of 'print' function
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/// let logger = result.clone();
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/// engine.on_debug(move |s, src, pos| logger.write().unwrap().push_str(
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/// &format!("{} @ {:?} > {}", src.unwrap_or("unknown"), pos, s)
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/// ));
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///
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/// let mut ast = engine.compile(r#"let x = "hello"; debug(x);"#)?;
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/// ast.set_source("world");
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/// engine.run_ast(&ast)?;
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///
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/// #[cfg(not(feature = "no_position"))]
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/// assert_eq!(*result.read().unwrap(), r#"world @ 1:18 > "hello""#);
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/// #[cfg(feature = "no_position")]
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/// assert_eq!(*result.read().unwrap(), r#"world @ none > "hello""#);
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/// # Ok(())
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/// # }
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/// ```
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#[inline(always)]
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pub fn on_debug(
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&mut self,
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callback: impl Fn(&str, Option<&str>, Position) + SendSync + 'static,
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) -> &mut Self {
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self.debug = Some(Box::new(callback));
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self
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}
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}
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