Skip to main content

weekly 2023-11-13

· 2 min read

In November 2023, MoonBit underwent Alpha testing. This post aims to introduce recent updates to MoonBit's language and toolchain, along with applications developed using MoonBit.

Changes in MoonBit Language

1. Performance improvement

  • Tokenization performance is improved around 25%.

  • Builtin comparison is inlined in an early stage which could have a large impact over a hotloop.

2. Syntax improvement

x := expr is discouraged in favor of the uniform let x = expr per the user feedback, the former grammer may be removed in the future.

3. Method calls on integers now require parentheses.

Before: 1.to_string()

After: (1).to_string()

4. Primitive types now support the hash method

Primitive types Bool, Char, Int, Int64, Double, String now support the hash method.


fn init {

// Output: 1042293711

5. Removed the built-in type Result、print_float64

  • Removed the built-in type Result. This type will be provided in the standard library in the future.
  • Removed print_float64 FFI. This function has been replaced by theprintlnfunction.


1. Support for users to customize runtime using JavaScript in the IDE

The IDE now supports users to customize runtime using JavaScript. For usage examples, please refer to the ffi folder at

2. Added a run button in the IDE

Added a run button in the IDE and changed the display of printed content from the Debug Console (DEBUG CONSOLE) to the Output Channel (OUTPUT).

3. Improved package support in the IDE

Previously, users could only run a package from amoon.pkg.jsonfile in that package. Now, any.mbtfile within a package can be used to run the package.

4.Added an option in the IDE to compile directly to wasm

Build System

  • Added moon build --debug option for adding debug information to the build output.

  • Adjusted the output directory ofmoon build. Now, depending on the build target and whether debug mode (--debug) is enabled, the output path of the build product is set to target/<arch>/<mode>.

CommandOutput directory
moon buildtarget/wasm/release
moon build --debugtarget/wasm/debug
moon build --target wasm-gctarget/wasm-gc/release
moon build --target wasm-gc --debugtarget/wasm-gc/debug