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https://github.com/valkmjolnir/nasal-interpreter
Modern efficient runtime for Nasal: using stack-based direct-threading virtual machine.
https://github.com/valkmjolnir/nasal-interpreter
bytecode-interpreter compiler-principles flightgear interpreter language linux macos nasal programming-language script-language scripting-language windows
Last synced: about 2 months ago
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Modern efficient runtime for Nasal: using stack-based direct-threading virtual machine.
- Host: GitHub
- URL: https://github.com/valkmjolnir/nasal-interpreter
- Owner: ValKmjolnir
- License: gpl-2.0
- Created: 2019-07-24T18:11:58.000Z (over 5 years ago)
- Default Branch: master
- Last Pushed: 2024-04-11T16:10:56.000Z (9 months ago)
- Last Synced: 2024-04-14T15:34:21.958Z (9 months ago)
- Topics: bytecode-interpreter, compiler-principles, flightgear, interpreter, language, linux, macos, nasal, programming-language, script-language, scripting-language, windows
- Language: C++
- Homepage: https://www.fgprc.org.cn/nasal_interpreter.html
- Size: 9.09 MB
- Stars: 49
- Watchers: 3
- Forks: 4
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# 
__Nasal - Modern Interpreter__
[](./LICENSE)
[](https://github.com/ValKmjolnir/Nasal-Interpreter/actions/workflows/c-cpp.yml)
> This document is also available in: [__中文__](./doc/README_zh.md) | [__English__](./README.md)
## __Contents__
* [__Introduction__](#introduction)
* [__Download__](#download)
* [__Compile__](#compile)
* [__Usage__](#how-to-use)
* [__Tutorial__](./doc/tutorial.md)
* [__Release Notes__](./doc/dev.md#release-notes)
* [__Development History__](./doc/dev.md)
* [__Benchmark__](./doc/benchmark.md)
* [__Difference__](#difference-between-andys-and-this-interpreter)
* [__Trace Back Info__](#trace-back-info)
* [__Debugger__](#debugger)
* [__REPL__](#repl)
* [__Web Interface__](#web-interface)
__Contact us if having great ideas to share!__
* [email protected]__ (ValKmjolnir)
* [email protected]__ (Sidi)
## __Introduction__
[Nasal](http://wiki.flightgear.org/Nasal_scripting_language)
is an ECMAscript-like language used in [FlightGear](https://www.flightgear.org/).
The designer is [Andy Ross](https://github.com/andyross).
This interpreter is rewritten by [ValKmjolnir](https://github.com/ValKmjolnir) using `C++`(`-std=c++17`).
We really appreciate that Andy created this amazing programming language: [Andy Ross's nasal interpreter](https://github.com/andyross/nasal).
Old version of this project uses __MIT license__ (2019/7 ~ 2021/5/4 ~ 2023/5). Now it uses __GPL v2 license__ (since 2023/6).
### __Why writing this Nasal interpreter?__
2019 summer,
members in [FGPRC](https://www.fgprc.org/) told me that it is hard to debug with nasal-console in Flightgear,
especially when checking syntax errors.
So i wrote a new interpreter to help checking syntax error and runtime error.
I wrote the lexer, parser and
bytecode virtual machine to help checking errors.
We found it much easier to debug.
You could also use this language to write some
interesting programs and run them without the lib of Flightgear.
You could add your own modules to make
the interpreter a useful tool in your own projects.
## __Download__
Nightly build could be found here.
Windows nightly build is not supported yet,
please wait or just compile it by yourself, a Cmake file is given for Visual Studio to compile this project easily:
* [MacOS-nightly-build](https://github.com/ValKmjolnir/Nasal-Interpreter/releases/tag/next_macOS)
* [Linux-nightly-build](https://github.com/ValKmjolnir/Nasal-Interpreter/releases/tag/next_linux_x86_64)
* [Windows-nightly-build](#download) [WIP]
## __Compile__
  
Download the latest source of the interpreter and build it! It's quite easy to build, what you need are only two things: C++ compiler and the `make`. There is no third-party library used in this project.
### __Windows (MinGW-w64)__
Make sure thread model is `posix thread model`, otherwise no thread library exists.
> mingw32-make nasal.exe -j4
### __Windows (Visual Studio)__
There is a [__CMakelists.txt__](./CMakeLists.txt) to create project.
### __Linux / macOS / Unix__
 
> make -j
You could choose which compiler you want to use:
> make nasal CXX=... -j
## __How to Use__
If your system is `Windows` and you want to output unicode, you could write this in nasal code:
```javascript
if (os.platform()=="windows") {
system("chcp 65001");
}
```
Or use `std.runtime.windows.set_utf8_output()`:
```javascript
use std.runtime;
runtime.windows.set_utf8_output();
```
## __Difference Between Andy's and This Interpreter__
Must use `var` to define variables
This interpreter uses more strict syntax to make sure it is easier for you to program and debug.
And flightgear's nasal interpreter also has the same rule.
So do not use variable without using `var` to declare it.
In Andy's interpreter:
```javascript
foreach(i; [0, 1, 2, 3])
print(i)
```
This program can run normally.
But take a look at the iterator `i`,
it is defined in foreach without using keyword `var`.
I think this design will make programmers feeling confused that they maybe hard to find the `i` is defined here.
Without `var`, they may think this `i` is defined anywhere else.
So in this interpreter i use a more strict syntax to force users to use `var` to define iterator of forindex and foreach.
If you forget to add the keyword `var`, you will get this:
```javascript
code: undefined symbol "i"
--> test.nas:1:9
|
1 | foreach(i; [0, 1, 2, 3])
| ^ undefined symbol "i"
code: undefined symbol "i"
--> test.nas:2:11
|
2 | print(i)
| ^ undefined symbol "i"
```
## __Trace Back Info__
When interpreter crashes,
it will print trace back information:
Native function `die`
Function `die` is used to throw error and crash immediately.
```javascript
func() {
println("hello");
die("error occurred this line");
return;
}();
```
```javascript
hello
[vm] error: error occurred this line
[vm] error: error occurred in native function
call trace (main)
call func@0x557513935710() {entry: 0x850}
trace back (main)
0x000547 4c 00 00 16 callb 0x16 <__die@0x557512441780>(std/lib.nas:150)
0x000856 4a 00 00 01 callfv 0x1(a.nas:3)
0x00085a 4a 00 00 00 callfv 0x0(a.nas:5)
stack (0x5575138e8c40, limit 10, total 14)
0x00000d | null |
0x00000c | pc | 0x856
0x00000b | addr | 0x5575138e8c50
0x00000a | nil |
0x000009 | nil |
0x000008 | str | <0x5575138d9190> error occurred t...
0x000007 | nil |
0x000006 | func | <0x5575139356f0> entry:0x850
0x000005 | pc | 0x85a
0x000004 | addr | 0x0
```
Stack overflow
Here is an example of stack overflow:
```javascript
func(f) {
return f(f);
}(
func(f) {
f(f);
}
)();
```
```javascript
[vm] error: stack overflow
call trace (main)
call func@0x564106058620(f) {entry: 0x859}
--> 583 same call(s)
call func@0x5641060586c0(f) {entry: 0x851}
trace back (main)
0x000859 45 00 00 01 calll 0x1(a.nas:5)
0x00085b 4a 00 00 01 callfv 0x1(a.nas:5)
0x00085b 582 same call(s)
0x000853 4a 00 00 01 callfv 0x1(a.nas:2)
0x00085f 4a 00 00 01 callfv 0x1(a.nas:3)
stack (0x56410600be00, limit 10, total 4096)
0x000fff | func | <0x564106058600> entry:0x859
0x000ffe | pc | 0x85b
0x000ffd | addr | 0x56410601bd20
0x000ffc | nil |
0x000ffb | nil |
0x000ffa | func | <0x564106058600> entry:0x859
0x000ff9 | nil |
0x000ff8 | func | <0x564106058600> entry:0x859
0x000ff7 | pc | 0x85b
0x000ff6 | addr | 0x56410601bcb0
```
Normal vm error crash info
Error will be thrown if there's a fatal error when executing:
```javascript
func() {
return 0;
}()[1];
```
```javascript
[vm] error: must call a vector/hash/string but get number
trace back (main)
0x000854 47 00 00 00 callv 0x0(a.nas:3)
stack (0x564993f462b0, limit 10, total 1)
0x000000 | num | 0
```
Detailed crash info
Use command __`-d`__ or __`--detail`__ the trace back info will show more details:
```javascript
hello
[vm] error: error occurred this line
[vm] error: error occurred in native function
call trace (main)
call func@0x55dcb5b8fbf0() {entry: 0x850}
trace back (main)
0x000547 4c 00 00 16 callb 0x16 <__die@0x55dcb3c41780>(std/lib.nas:150)
0x000856 4a 00 00 01 callfv 0x1(a.nas:3)
0x00085a 4a 00 00 00 callfv 0x0(a.nas:5)
stack (0x55dcb5b43120, limit 10, total 14)
0x00000d | null |
0x00000c | pc | 0x856
0x00000b | addr | 0x55dcb5b43130
0x00000a | nil |
0x000009 | nil |
0x000008 | str | <0x55dcb5b33670> error occurred t...
0x000007 | nil |
0x000006 | func | <0x55dcb5b8fbd0> entry:0x850
0x000005 | pc | 0x85a
0x000004 | addr | 0x0
registers (main)
[pc ] | pc | 0x547
[global] | addr | 0x55dcb5b53130
[local ] | addr | 0x55dcb5b43190
[memr ] | addr | 0x0
[canary] | addr | 0x55dcb5b53110
[top ] | addr | 0x55dcb5b431f0
[funcr ] | func | <0x55dcb5b65620> entry:0x547
[upval ] | nil |
global (0x55dcb5b53130)
0x000000 | nmspc| <0x55dcb5b33780> namespace [95 val]
0x000001 | vec | <0x55dcb5b64c20> [0 val]
...
0x00005e | func | <0x55dcb5b8fc70> entry:0x846
local (0x55dcb5b43190 <+7>)
0x000000 | nil |
0x000001 | str | <0x55dcb5b33670> error occurred t...
0x000002 | nil |
```
## __Debugger__
We added a debugger in `v8.0`.
Use command `./nasal -dbg xxx.nas` to use the debugger,
and the debugger will print this:
Click to unfold
```javascript
source code:
--> var fib = func(x) {
if (x<2) return x;
return fib(x-1)+fib(x-2);
}
for(var i=0;i<31;i+=1)
print(fib(i),'\n');
next bytecode:
0x0003a8 07:00 00 00 00 00 00 00 00 pnil 0x0 (std/lib.nas:413)
0x0003a9 56:00 00 00 00 00 00 00 00 ret 0x0 (std/lib.nas:413)
0x0003aa 03:00 00 00 00 00 00 00 56 loadg 0x56 (std/lib.nas:413)
--> 0x0003ab 0b:00 00 00 00 00 00 03 af newf 0x3af (test/fib.nas:1)
0x0003ac 02:00 00 00 00 00 00 00 03 intl 0x3 (test/fib.nas:1)
0x0003ad 0d:00 00 00 00 00 00 00 22 para 0x22 (x) (test/fib.nas:1)
0x0003ae 3e:00 00 00 00 00 00 03 be jmp 0x3be (test/fib.nas:1)
0x0003af 45:00 00 00 00 00 00 00 01 calll 0x1 (test/fib.nas:2)
vm stack (0x7fca7e9f1010, limit 16, total 0)
>>
```
If want help, input `h` to get help.
When running the debugger, you could see what is on stack.
This will help you debugging or learning how the vm works:
Click to unfold
```javascript
source code:
var fib = func(x) {
--> if (x<2) return x;
return fib(x-1)+fib(x-2);
}
for(var i=0;i<31;i+=1)
print(fib(i),'\n');
next bytecode:
0x0003a8 07:00 00 00 00 00 00 00 00 pnil 0x0 (std/lib.nas:413)
0x0003a9 56:00 00 00 00 00 00 00 00 ret 0x0 (std/lib.nas:413)
0x0003aa 03:00 00 00 00 00 00 00 56 loadg 0x56 (std/lib.nas:413)
0x0003ab 0b:00 00 00 00 00 00 03 af newf 0x3af (test/fib.nas:1)
0x0003ac 02:00 00 00 00 00 00 00 03 intl 0x3 (test/fib.nas:1)
0x0003ad 0d:00 00 00 00 00 00 00 22 para 0x22 (x) (test/fib.nas:1)
0x0003ae 3e:00 00 00 00 00 00 03 be jmp 0x3be (test/fib.nas:1)
--> 0x0003af 45:00 00 00 00 00 00 00 01 calll 0x1 (test/fib.nas:2)
vm stack (0x7fca7e9f1010, limit 16, total 8)
0x000007 | pc | 0x3c7
0x000006 | addr | 0x0
0x000005 | nil |
0x000004 | nil |
0x000003 | num | 0
0x000002 | nil |
0x000001 | nil |
0x000000 | func | <0x5573f66ef5f0> func(elems...) {..}
>>
```
## REPL
We added experimental repl interpreter in v11.0.
Use this command to use the repl interpreter:
> nasal -r
Then enjoy!
```bash
[nasal-repl] Initializating enviroment...
[nasal-repl] Initialization complete.
Nasal REPL interpreter version 11.0 (Oct 7 2023 17:28:31)
.h, .help | show help
.e, .exit | quit the REPL
.q, .quit | quit the REPL
.c, .clear | clear the screen
.s, .source | show source code
>>>
```
Try import `std/json.nas`~
```bash
[nasal-repl] Initializating enviroment...
[nasal-repl] Initialization complete.
Nasal REPL interpreter version 11.1 (Nov 1 2023 23:37:30)
.h, .help | show help
.e, .exit | quit the REPL
.q, .quit | quit the REPL
.c, .clear | clear the screen
.s, .source | show source code
>>> use std.json;
{stringify:func(..) {..},parse:func(..) {..}}
>>>
```
## __Web Interface__
A web-based interface is now available for trying out Nasal code directly in your browser. It includes both a code editor and an interactive REPL (WIP).
### Web Code Editor
- Syntax highlighting using CodeMirror
- Error highlighting and formatting
- Example programs
- Execution time display option
- Configurable execution time limits
- Notice: The security of the online interpreter is not well tested, please use it with sandbox mechanism or other security measures.
### Web REPL
- ** IMPORTANT: The time limit in REPL is not correctly implemented yet. Thus this REPL web binding is not considered finished. Do not use it in production before it's fixed. **
- Interactive command-line style interface in browser
- Multi-line input support with proper prompts (`>>>` and `...`)
- Command history navigation
- Error handling with formatted error messages
- Example snippets for quick testing
### Running the Web Interface
1. Build the Nasal shared library:
```bash
cmake -DBUILD_SHARED_LIBS=ON .
make nasal-web
```
2. Set up and run the web application:
For the code editor:
```bash
cd nasal-web-app
npm install
node server.js
```
Visit `http://127.0.0.1:3000/`
For the REPL:
```bash
cd nasal-web-app
npm install
node server_repl.js
```
Visit `http://127.0.0.1:3001/repl.html`