ksl 0.1.7

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

use crate::{Environment, MODULE_NAME_ENV, value::Value};

pub(crate) fn builtin(args: &[Value], env: &Environment) -> Option<(Value, Environment)> {
    if let [Value::String(module_name)] = &args[..] {
        if let Some(Value::String(previous_name)) = env.get(MODULE_NAME_ENV) {
            eprintln!(
                concat!(
                    "Error[ksl::builtin::module]: ",
                    "Current module is already bound as {}.",
                ),
                previous_name
            );
            None
        } else {
            Some((
                Value::Unit,
                Environment::from([(
                    String::from(MODULE_NAME_ENV),
                    Value::String(module_name.clone()),
                )]),
            ))
        }
    } else {
        eprintln!(
            concat!(
                "Error[ksl::builtin::module]: ",
                "Only accepts a string as arguments, but {:?} were passed."
            ),
            args
        );
        None
    }
}