The Berry Script Language.

Introduction

Berry is a ultra-lightweight dynamically typed embedded scripting language. It is designed for lower-performance embedded devices. The Berry interpreter-core's code size is less than 40KiB and can run on less than 4KiB heap (on ARM Cortex M4 CPU, Thumb ISA and ARMCC compiler).

The interpreter of Berry include a one-pass compiler and register-based VM, all the code is written in ANSI C99. In Berry not every type is a class object. Some simple value types, such as int, real, boolean and string are not class object, but list, map and range are class object. This is a consideration about performance. Register-based VM is the same meaning as above.

Berry has the following advantages:

• Lightweight: A well-optimized interpreter with very little resources. Ideal for use in microprocessors.
• Fast: optimized one-pass bytecode compiler and register-based virtual machine.
• Powerful: supports imperative programming, object-oriented programming, functional programming.
• Flexible: Berry is a dynamic type script, and it's intended for embedding in applications. It can provide good dynamic scalability for the host system.
• Simple: simple and natural syntax, support garbage collection, and easy to use FFI (foreign function interface).
• RAM saving: With compile-time object construction, most of the constant objects are stored in read-only code data segments, so the RAM usage of the interpreter is very low when it starts.

Documents

LaTeX documents repository: https://github.com/Skiars/berry_doc

Reference Manual: berry_rm_zh_cn.pdf (Simplified Chinese version)

Berry's EBNF grammar definition: tools/grammar/berry.ebnf

Features

• Base Type
  • Numerical value: Integer (int) and Real (real)
  • Boolean: true and false
  • String: Single quotation-mark string and double quotation-mark string
  • List: Continuous memory list, like [1, 2, 3]
  • Map: Hash Map, like { 'a': 1, 2: 3, 'map': {} }
  • Range: include a lower and a upper integer value, like 0..5
• Operator and Expression
  • Assign operator: =, +=, -=, *=, /=, %=, &=, |=, ^=, <<=, >>=
  • Relational operator: <, <=, ==, !=, >, >=
  • Logic operator: &&, ||, !
  • Arithmetic operator: +, -, *, /, %
  • Bitwise operator: &, |, ~, ^, <<, >>
  • Field operator: .
  • Subscript operator: []
  • Connect string operator: +
  • Conditional operator: ? :
  • Brackets: ()
• Control Structure
  • Conditional statement: if-else
  • Iteration statement: while and for
  • Jump statement: break and continue
• Function
  • Local variable and block scope
  • Return statement
  • Nested functions definition
  • Closure based on Upvalue
  • Anonymous function
  • Lambda expression
• Class
  • Inheritance (only public single inheritance)
  • Method and Operator Overload
  • Constructor method
  • Destructive method
• Module Management
  • Built-in module that takes almost no RAM
  • Extension module support: script module, bytecode file module and shared library (like *.so, *.dll) module
• GC (Garbage collection)
  • Mark-Sweep GC
• Exceptional Handling
  • Throw any exception value using the raise statement
  • Multiple catch mode
• Bytecode file support
  • Export function to bytecode file
  • Load the bytecode file and execute

Build and Run

1. Install the readline library (Windows does not need):

   sudo apt install libreadline-dev # Ubuntu
   brew install readline            # MacOS

2. Build (The default compiler is GCC):

   make
   

3. Run:

   ./berry # Bash or PowerShell
   berry   # Windows CMD

4. Install (Only Unix-like):

   make install

Editor pulgins

Visual Studio Code pulgin are in this directory: ./tools/pulgins/vscode.

Examples

After compiling successfully, use the berry command with no parameters to enter the REPL environment:

Berry 0.0.1 (build in Dec 24 2018, 18:12:49)
[GCC 8.2.0] on Linux (default)
>

Now enter this code:

print("Hello world!")

You will see this output:

Hello world!

You can copy this code to the REPL:

def fib(x)
    if x <= 1
        return x
    end
    return fib(x - 1) + fib(x - 2)
end
fib(10)

This example code will output the result 55, and you can save the above code to a plain text file (eg test.be) and run this command:

./berry test.be

This will also get the correct output.