ksl 0.1.30

KSL core library and interpreter
Documentation 
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//! # ksl::builtin::find
//!
//! Built-in function `Find`.

use crate::{Environment, eval::apply::eval_apply, value::Value};

pub(crate) fn builtin(args: &[Value], env: Environment) -> Result<Value, std::sync::Arc<str>> {
    if let [list, element] = args {
        match (eval_apply(list, env.clone())?, eval_apply(element, env)?) {
            (Value::List(elements), e) => match elements.iter().position(|element| element == &e) {
                Some(pos) => Ok(Value::Number((pos + 1) as f64)),
                None => Ok(Value::Number(0.0)),
            },

            (e, _) => Err(std::sync::Arc::from(format!(
                concat!("Error[ksl::builtin::Find]: ", "Unexpected value: `{}`."),
                e
            ))),
        }
    } else {
        Err(std::sync::Arc::from(format!(
            concat!(
                "Error[ksl::builtin::Find]: ",
                "Expected 2 parameters, but {} were passed."
            ),
            args.len()
        )))
    }
}