ksl 0.1.30

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

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

pub(crate) fn builtin(args: &[Value], env: Environment) -> Result<Value, std::sync::Arc<str>> {
    match args {
        [sym_expr] => match sym_expr {
            Value::Symbol(var_sym) => {
                let exists = read_from_environment(&env, var_sym).is_some();
                Ok(if exists {
                    TRUE_SYMBOL.clone()
                } else {
                    FALSE_SYMBOL.clone()
                })
            }
            e => Err(std::sync::Arc::from(format!(
                "Error[ksl::builtin::Has]: Expected a Symbol, but got `{}`.",
                e
            ))),
        },

        [obj_expr, key_expr] => {
            let obj_val = eval_apply(obj_expr, env.clone())?;
            let key_val = eval_apply(key_expr, env.clone())?;

            match (obj_val, key_val) {
                (Value::Object(_, dict), Value::Atom(key)) => {
                    let exists = dict.contains_key(&key);
                    Ok(if exists {
                        TRUE_SYMBOL.clone()
                    } else {
                        FALSE_SYMBOL.clone()
                    })
                }
                (Value::Object(_, _), e) => Err(std::sync::Arc::from(format!(
                    "Error[ksl::builtin::Has]: Expected an Atom for the key, but got `{}`.",
                    e
                ))),
                (e, _) => Err(std::sync::Arc::from(format!(
                    "Error[ksl::builtin::Has]: Expected an Object, but got `{}`.",
                    e
                ))),
            }
        }
        _ => Err(std::sync::Arc::from(format!(
            concat!(
                "Error[ksl::builtin::Has]: ",
                "Expected 1 or 2 parameters, but {} were passed."
            ),
            args.len()
        ))),
    }
}