Merge pull request #91 from jakubdabek/90_function_fn_clone

Make `Function` able to hold capturing closures.

Closes #90.
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ISibboI 2021-08-16 13:30:22 +03:00 committed by GitHub
commit 3aef19e71b
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2 changed files with 69 additions and 5 deletions

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@ -4,6 +4,26 @@ use crate::{error::EvalexprResult, value::Value};
pub(crate) mod builtin; pub(crate) mod builtin;
/// A helper trait to enable cloning through `Fn` trait objects.
trait ClonableFn
where
Self: Fn(&Value) -> EvalexprResult<Value>,
Self: Send + Sync + 'static,
{
fn dyn_clone(&self) -> Box<dyn ClonableFn>;
}
impl<F> ClonableFn for F
where
F: Fn(&Value) -> EvalexprResult<Value>,
F: Send + Sync + 'static,
F: Clone,
{
fn dyn_clone(&self) -> Box<dyn ClonableFn> {
Box::new(self.clone()) as _
}
}
/// A user-defined function. /// A user-defined function.
/// Functions can be used in expressions by storing them in a `Context`. /// Functions can be used in expressions by storing them in a `Context`.
/// ///
@ -18,17 +38,31 @@ pub(crate) mod builtin;
/// })).unwrap(); // Do proper error handling here /// })).unwrap(); // Do proper error handling here
/// assert_eq!(eval_with_context("id(4)", &context), Ok(Value::from(4))); /// assert_eq!(eval_with_context("id(4)", &context), Ok(Value::from(4)));
/// ``` /// ```
#[derive(Clone)]
pub struct Function { pub struct Function {
function: fn(&Value) -> EvalexprResult<Value>, function: Box<dyn ClonableFn>,
}
impl Clone for Function {
fn clone(&self) -> Self {
Self {
function: self.function.dyn_clone(),
}
}
} }
impl Function { impl Function {
/// Creates a user-defined function. /// Creates a user-defined function.
/// ///
/// The `function` is a boxed function that takes a `Value` and returns a `EvalexprResult<Value, Error>`. /// The `function` is boxed for storage.
pub fn new(function: fn(&Value) -> EvalexprResult<Value>) -> Self { pub fn new<F>(function: F) -> Self
Self { function } where
F: Fn(&Value) -> EvalexprResult<Value>,
F: Send + Sync + 'static,
F: Clone,
{
Self {
function: Box::new(function) as _,
}
} }
pub(crate) fn call(&self, argument: &Value) -> EvalexprResult<Value> { pub(crate) fn call(&self, argument: &Value) -> EvalexprResult<Value> {

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@ -276,6 +276,36 @@ fn test_n_ary_functions() {
); );
} }
#[test]
fn test_capturing_functions() {
let mut context = HashMapContext::new();
// this variable is captured by the function
let three = 3;
context
.set_function(
"mult_3".into(),
Function::new(move |argument| {
if let Value::Int(int) = argument {
Ok(Value::Int(int * three))
} else if let Value::Float(float) = argument {
Ok(Value::Float(float * three as f64))
} else {
Err(EvalexprError::expected_number(argument.clone()))
}
}),
)
.unwrap();
let four = 4;
context
.set_function("function_four".into(), Function::new(move |_| Ok(Value::Int(four))))
.unwrap();
assert_eq!(eval_with_context("mult_3 2", &context), Ok(Value::Int(6)));
assert_eq!(eval_with_context("mult_3(3)", &context), Ok(Value::Int(9)));
assert_eq!(eval_with_context("mult_3(function_four())", &context), Ok(Value::Int(12)));
}
#[test] #[test]
fn test_builtin_functions() { fn test_builtin_functions() {
// Log // Log