6be3b7d80e
This commit "reverts" a change introduced in bee98999,
by making `Function` be simultaneously `Fn` and `Clone`.
84 lines
1.9 KiB
Rust
84 lines
1.9 KiB
Rust
use std::fmt;
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use crate::{error::EvalexprResult, value::Value};
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pub(crate) mod builtin;
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/// A helper trait to enable cloning through `Fn` trait objects.
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trait ClonableFn
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where
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Self: Fn(&Value) -> EvalexprResult<Value>,
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Self: Send + Sync + 'static,
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{
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fn dyn_clone(&self) -> Box<dyn ClonableFn>;
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}
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impl<F> ClonableFn for F
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where
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F: Fn(&Value) -> EvalexprResult<Value>,
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F: Send + Sync + 'static,
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F: Clone,
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{
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fn dyn_clone(&self) -> Box<dyn ClonableFn> {
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Box::new(self.clone()) as _
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}
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}
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/// A user-defined function.
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/// Functions can be used in expressions by storing them in a `Context`.
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///
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/// # Examples
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///
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/// ```rust
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/// use evalexpr::*;
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///
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/// let mut context = HashMapContext::new();
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/// context.set_function("id".into(), Function::new(|argument| {
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/// Ok(argument.clone())
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/// })).unwrap(); // Do proper error handling here
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/// assert_eq!(eval_with_context("id(4)", &context), Ok(Value::from(4)));
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/// ```
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pub struct Function {
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function: Box<dyn ClonableFn>,
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}
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impl Clone for Function {
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fn clone(&self) -> Self {
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Self {
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function: self.function.dyn_clone(),
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}
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}
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}
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impl Function {
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/// Creates a user-defined function.
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///
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/// The `function` is boxed for storage.
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pub fn new<F>(function: F) -> Self
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where
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F: Fn(&Value) -> EvalexprResult<Value>,
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F: Send + Sync + 'static,
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F: Clone,
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{
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Self {
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function: Box::new(function) as _,
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}
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}
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pub(crate) fn call(&self, argument: &Value) -> EvalexprResult<Value> {
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(self.function)(argument)
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}
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}
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impl fmt::Debug for Function {
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fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
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write!(f, "Function {{ [...] }}")
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}
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}
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/// A trait to ensure a type is `Send` and `Sync`.
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/// If implemented for a type, the crate will not compile if the type is not `Send` and `Sync`.
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trait IsSendAndSync: Send + Sync {}
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impl IsSendAndSync for Function {}
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