The EndBASIC programming language - core

EndBASIC is an interpreter for a BASIC-like language and is inspired by Amstrad's Locomotive BASIC 1.1 and Microsoft's QuickBASIC 4.5. Like the former, EndBASIC intends to provide an interactive environment that seamlessly merges coding with immediate visual feedback. Like the latter, EndBASIC offers higher-level programming constructs and strong typing.

EndBASIC offers a simplified and restricted environment to learn the foundations of programming and focuses on features that can quickly reward the programmer. These features include things like a built-in text editor, commands to render graphics, and commands to interact with the hardware of a Raspberry Pi. Implementing this kind of features has priority over others such as performance or a much richer language.

EndBASIC is written in Rust and runs both on the web and locally on a variety of operating systems and platforms, including macOS, Windows, and Linux.

EndBASIC is free software under the Apache 2.0 License.

What's in this crate?

endbasic-core provides the language parser and interpreter. By design, this crate provides zero commands and zero functions.

Language features

EndBASIC's language features are inspired by other BASIC interpreters but the language does not intend to be fully compatible with them. The language currently supports:

• Variable types: boolean (?), double (#), integer (%), and string ($).
• Arrays via DIM name(1, 2, 3) AS type.
• Strong typing with optional variable type annotations.
• DATA statements for literal primitive values. Booleans, numbers, and strings are supported, but strings must be double-quoted.
• DO / LOOP statements with optional UNTIL / WHILE pre- and post-guards and optional EXIT DO early terminations.
• DIM SHARED for global variables.
• FUNCTION name / END FUNCTION.
• IF ... THEN ... [ELSE ...] uniline statements.
• IF ... THEN / ELSEIF ... THEN / ELSE / END IF multiline statements.
• FOR x = ... TO ... [STEP ...] / NEXT loops.
• GOSUB line / GOSUB @label / RETURN for procedure execution.
• GOTO line / GOTO @label statements and @label annotations.
• SELECT CASE / CASE ... / CASE IS ... / CASE ... TO ... / END SELECT statements.
• SUB name / END SUB.
• WHILE ... / WEND loops.
• Error handling via ON ERROR GOTO and ON ERROR RESUME NEXT.
• UTF-8 everywhere (I think).

Design principles

Some highlights about the EndBASIC implementation are:

• Minimalist core. The interpreter knows how to execute the logic of the language but, by default, it exposes no builtins to the scripts—not even INPUT or PRINT. This makes EndBASIC ideal for embedding into other programs, as it is possible to execute external code without side-effects or by precisely controlling how such code interacts with the host program.

• Async support. The interpreter is async-compatible, making it trivial to embed it into Javascript via WASM.

Examples

The examples directory contains sample code to show how to embed the EndBASIC interpreter into your own programs. In particular:

• examples/config.rs: Shows how to instantiate a minimal EndBASIC interpreter and uses it to implement what could be a configuration file parser.

• examples/dsl.rs: Shows how to instantiate an EndBASIC interpreter with custom functions and commands to construct what could be a domain-specific language. This language is then used to control some hypothetical hardware lights and exemplifies how to bridge the Rust world and the EndBASIC world.