ksl 0.1.5

KSL core library and interpreter
Documentation 
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use crate::{Environment, FALSE_SYMBOL, TRUE_SYMBOL, eval::apply::eval_apply, value::Value};

pub(crate) fn builtin(args: &[Value], env: &Environment) -> Option<(Value, Environment)> {
    if let [v1, v2] = &args[..] {
        match eval_apply(v1, env) {
            Some((Value::Atom(p1), _)) if &p1 == FALSE_SYMBOL => match eval_apply(v2, env) {
                Some((e, _)) => Some((e, Environment::new())),
                None => {
                    eprintln!(
                        concat!(
                            "Error[ksl::builtin::or]: ",
                            "Cannot evaluate expression {:?}."
                        ),
                        v2
                    );
                    None
                }
            },
            Some((Value::Atom(p1), _)) if &p1 == TRUE_SYMBOL => {
                Some((Value::Atom(p1), Environment::new()))
            }
            Some((e, _)) => {
                eprintln!(
                    concat!(
                        "Error[ksl::builtin::or]: ",
                        "Expected a boolean, but got `{:?}`."
                    ),
                    e
                );
                None
            }
            None => {
                eprintln!(
                    concat!(
                        "Error[ksl::builtin::or]: ",
                        "Cannot evaluate expression {:?}."
                    ),
                    v1
                );
                None
            }
        }
    } else {
        eprintln!(
            concat!(
                "Error[ksl::builtin::or]: ",
                "Only accepts 2 arguments, but {} were passed."
            ),
            args.len()
        );
        None
    }
}