ksl 0.1.5

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

pub(crate) fn builtin(args: &[Value], env: &Environment) -> Option<(Value, Environment)> {
    if let [module, Value::Identity(symbol)] = &args[..] {
        match eval_apply(module, env) {
            Some((Value::Module(name, mdoule_env), _)) => match mdoule_env.get(symbol) {
                Some(val) => Some((val.clone(), Environment::new())),
                None => {
                    eprintln!(
                        concat!(
                            "Error[ksl::builtin::use]: ",
                            "Symbol `{}` is not bound in module `{}`."
                        ),
                        symbol, name
                    );
                    None
                }
            },
            Some((e, _)) => {
                eprintln!(
                    concat!(
                        "Error[ksl::builtin::use]: ",
                        "Expected a module, but got `{:?}`."
                    ),
                    e
                );
                None
            }
            None => {
                eprintln!(
                    concat!(
                        "Error[ksl::builtin::use]: ",
                        "Cannot evaluate expression {:?}."
                    ),
                    module
                );
                None
            }
        }
    } else {
        eprintln!(
            concat!(
                "Error[ksl::builtin::use]: ",
                "Only accepts a module and a symbol as arguments, but got {:?}.",
            ),
            args
        );
        None
    }
}