BASON
A lightweight AST (abstract syntax tree) interpreter built in javascript.
BASON is an acronym for Basic Abstract Syntax Object Notation.
Syntax
While BASON does not include a parser, You can write programs directly in JSON.
- A
Program
in BASON is contstructed as a valid JSON object and contains a script - A
Script
is an array of expressions to be evaluated. - An
Expression
is a literal (string
ornumber
), or an object who's key is a keyword (Command
,Function
, orVariable
) and value is its input parameter(s). Parameters
are also an array of expressions. If there's only one parameter, there's no need for the containing array.- If you're looking for a simpler syntax, check out the bason-funky parser
Examples
Hello World:
"PRINT": "Hello World!"
Each program is an array of expressions, and therefore wrapped in square brackets. This script only has one expression, an object whos key is the name of the command, in this case PRINT
, and we supply it with a string literal which results in the text "Hello World!" printing to the console.
Using Variables:
"LET": "myvar" "World!" "PRINT": "ADD": "Hello " "myvar": null
In this example we define a variable with the LET
command which takes two parameters: the name of the variable and its value. We then use the ADD
function to join the text "Hello " with the value of myvar
to get "Hello World!" In BASON Script, Variables are referenced as objects with a null
value.
Using Loops:
"LET": "i" 0 "REPEAT": 10 "script": "SET": "i" "ADD": "i": null 1 "PRINT": "i": null
This program prints the numbers 1 to 10 to the console using the REPEAT
command. Any command which executes a script such as loops takes a special object property called "script" who's value is a script
array.
Functions:
"FUNCTION": "GREET" "name" "script": "PRINT": "ADD": "Hello " "name": null "GREET": "Dan"
Here we define a new function called GREET
with an input parameter called name
. Once it has been defined, we can use it the same as any other command. Presently, functions are not hoisted, so you must declare a function before it is used in a script.
Functions are locally scoped, so any variables or functions declared in them will not be accessible outside and will shadow anything of the same name in the outer scope.
Language
But why?
BASON's syntax is obviously painful to write, so why would you want to use it? Well it has a couple of interesting use cases:
- A safe method of transmitting and executing arbitrary server-side code in a sand-boxed environment.
- BASON's data format is an Abstract Syntax Tree, making it an ideal target interpreter for creating new languages and parsers.
Installation
npm install bason --save
Usage
Import the package, define your program, and run it with BASON.RUN()
let BASON = let program = "LET": "myvar" "World!" "PRINT": "ADD": "Hello " "myvar": null BASON;
Running the Demo
npm run demo
will run the example program located in demo/index.js