62 lines
1.7 KiB
Rust
62 lines
1.7 KiB
Rust
use std::fmt;
|
|
|
|
use error::{self, EvalexprResult};
|
|
use value::Value;
|
|
|
|
pub(crate) mod builtin;
|
|
|
|
/// A user-defined function.
|
|
/// Functions can be used in expressions by storing them in a `Context`.
|
|
///
|
|
/// # Examples
|
|
///
|
|
/// ```rust
|
|
/// use evalexpr::*;
|
|
///
|
|
/// let mut context = HashMapContext::new();
|
|
/// context.set_function("id".into(), Function::new(Some(1), Box::new(|arguments| {
|
|
/// Ok(arguments[0].clone())
|
|
/// }))).unwrap(); // Do proper error handling here
|
|
/// assert_eq!(eval_with_context("id(4)", &context), Ok(Value::from(4)));
|
|
/// ```
|
|
pub struct Function {
|
|
argument_amount: Option<usize>,
|
|
function: Box<Fn(&[Value]) -> EvalexprResult<Value>>,
|
|
}
|
|
|
|
impl Function {
|
|
/// Creates a user-defined function.
|
|
///
|
|
/// The `argument_amount` is the amount of arguments this function takes.
|
|
/// It is verified before the actual function is executed, assuming it is not `None`.
|
|
///
|
|
/// The `function` is a boxed function that takes a slice of values and returns a `EvalexprResult<Value, Error>`.
|
|
pub fn new(
|
|
argument_amount: Option<usize>,
|
|
function: Box<Fn(&[Value]) -> EvalexprResult<Value>>,
|
|
) -> Self {
|
|
Self {
|
|
argument_amount,
|
|
function,
|
|
}
|
|
}
|
|
|
|
pub(crate) fn call(&self, arguments: &[Value]) -> EvalexprResult<Value> {
|
|
if let Some(argument_amount) = self.argument_amount {
|
|
error::expect_function_argument_amount(arguments.len(), argument_amount)?;
|
|
}
|
|
|
|
(self.function)(arguments)
|
|
}
|
|
}
|
|
|
|
impl fmt::Debug for Function {
|
|
fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
|
|
write!(
|
|
f,
|
|
"Function {{ argument_amount: {:?}, function: [...] }}",
|
|
self.argument_amount
|
|
)
|
|
}
|
|
}
|