endbasic-core 0.4.0

The EndBASIC programming language - core
Documentation 
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// EndBASIC
// Copyright 2020 Julio Merino
//
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License.  You may obtain a copy
// of the License at:
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
// License for the specific language governing permissions and limitations
// under the License.

//! Minimal EndBASIC interpreter to process a script.
//!
//! This example sets up a minimal EndBASIC interpreter: that is, one without any builtin commands,
//! which makes parsing of any scripts free of side effects.  This could be used, for example, to
//! parse a configuration file---which is what is shown here.

use endbasic_core::exec::Machine;
use futures_lite::future::block_on;
use std::io;

/// Sample code to parse in this example.
const INPUT: &str = r#"
foo_value = 123
enable_bar = (foo_value > 122)
'enable_baz = "this is commented out"
"#;

fn main() {
    // Create an empty machine.
    let mut machine = Machine::default();

    // Execute the sample script.  All this script can do is modify the state of the machine itself.
    // In other words: the script can set variables in the machine's environment, but that's it.
    let mut cursor = io::Cursor::new(INPUT.as_bytes());
    block_on(machine.exec(&mut cursor)).expect("Execution error");

    // Now that our script has run, inspect the variables it set on the machine.
    match machine.get_var_as_int("foo_value") {
        Ok(i) => println!("foo_value is {}", i),
        Err(e) => println!("Input did not contain foo_value: {}", e),
    }
    match machine.get_var_as_bool("enable_bar") {
        Ok(b) => println!("enable_bar is {}", b),
        Err(e) => println!("Input did not contain enable_bar: {}", e),
    }
    match machine.get_var_as_string("enable_baz") {
        Ok(b) => println!("enable_bar is {}", b),
        Err(e) => println!("enable_baz is not set: {}", e),
    }
}