https://github.com/coyove/nj
NJ is a simple script engine in golang with Lua-like syntax.
https://github.com/coyove/nj
closure coroutine go interpreter lua script-language yield
Last synced: 8 months ago
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NJ is a simple script engine in golang with Lua-like syntax.
- Host: GitHub
- URL: https://github.com/coyove/nj
- Owner: coyove
- License: mit
- Created: 2018-04-17T23:52:58.000Z (almost 8 years ago)
- Default Branch: master
- Last Pushed: 2022-11-10T08:50:07.000Z (over 3 years ago)
- Last Synced: 2025-06-03T22:03:11.922Z (10 months ago)
- Topics: closure, coroutine, go, interpreter, lua, script-language, yield
- Language: Go
- Homepage:
- Size: 4.4 MB
- Stars: 17
- Watchers: 2
- Forks: 2
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
NJ is a simple script engine written in golang with Lua-like syntax.
(If you are looking for a Lua 5.2 compatible engine, refer to tag `v0.2`)
## Differ from Lua
- There is no `table`, instead there are `array` and `object` respectively:
- `a=[1, 2, 3]`.
- `a={a=1, b=2}`.
- Empty array and empty object are `true` when used as booleans.
- There are `typed` array and `untyped` array:
- Untyped arrays are generic arrays created by `[...]`, it is the builtin array type.
- Typed arrays are special arrays created by Go, say `[]byte`:
- `a = bytes(16)` creates a 16-byte long `[]byte`.
- `a.append(1)` appends 1 to it.
- `a.append(true)` will panic.
- `a.untype().append(true)` will `untype` the array into a (new) generic array.
- Functions are callable objects:
- `function foo() end; assert(type(foo), "object")`
- `function foo() end; assert(foo is callable)`
- Closures are created by capturing all symbols seen in the current scope and binding them to the returned function:
- `function foo(a, b) return function(c) return self.a + self.b + c end end`
- `assert(foo(1, 2)(3), 6)`
- Syntax of calling functions strictly requires no spaces between the callee and '(':
- `print(1)` is the only right way of calling a function.
- `print (1)` literally means two things: 1) get value of `print` and discard it, 2) evaluate `(1)`.
- Also note that all required arguments must be provided to call a function properly:
- `function foo(a, b) end; foo(1)` is invalid.
- Spacing rule also applies to unary operator `-`:
- `a = 1-a <=> a = 1 - a` means assign the result of `1-a` to `a`.
- `a = 1 -a` means assign `1` to `a` and negate `a`.
- `a = 1 -a+1` means assign `1` to `a` and eval `-a+1`.
- `a = -a` means negate `a` and assign the result to `a`.
- `a = - a` is invalid.
- There are two ways to write `if`:
- `if cond then true else false end` as a statement.
- `local a = if(cond, true, false)` as an expression.
- `if(cond) then ... end` is invalid, spaces after `if` statement is mandatory.
- `if (cond, true, false)` is invalid, spaces after `if` expression is not allowed.
- To write variadic functions:
- `function foo(a, b...) end; args = [1, 2, 3]; foo(args...)`.
- Parameters after `...` are optional:
- `function foo(a ... b, c) end; foo(1); foo(1, 2); foo(1, 2, 3)`
- Returning multiple arguments will be translated into returning an array, e.g.:
- `function foo() return 1, 2 end <=> function foo() return [1, 2] end`
- `local a, b, c = d <=> local a, b, c = d[0], d[1], d[2]`
- Everything starts at ZERO. For-loops start inclusively and end exclusively, e.g.:
- `a=[1, 2]; assert(a[0] == 1)`.
- `for i=0,n do ... end` ranges `[0, n-1]`.
- `for i=n-1,-1,-1 do ... end` ranges `[n-1, 0]`.
- For method function, it can access `this` which points to the receiver:
- `a={}; function a.foo(x) this.x = x end; a.foo(1); assert(a.x, 1)`
- For any function, use `self` to get itself in the body:
- `function foo(x) self.x = x end; foo(1); assert(foo.x, 1)`
- You can define up to 32000 variables (varies depending on the number of temporal variables generated by interpreter) in a function.
- Numbers are `int64 + float64` internally, interpreter may promote it to `float64` when needed and downgrade it to `int64` when possible.
- You can `return` anywhere inside functions, `continue` inside for-loops, `goto` any label within the same function.
## Run
```golang
program, err := nj.LoadString("return 1")
v, err := program.Run() // v == 1
```
### Global Values
```golang
bas.AddGlobal("G", bas.ValueOf(func() int { return 1 }))
program, _ := nj.LoadString("return G() + 1")
v, err := program.Run() // v == 2
program, _ = nj.LoadString("return G() + 2")
v, err = program.Run() // v == 3
program, _ = nj.LoadString("return G + 2", &CompileOptions{
Globals: bas.NewObject(0).SetProp("G", 10).ToMap(), // override the global 'G'
})
v, err = program.Run() // v == 12
```
## Benchmarks
Refer to [here](https://github.com/coyove/nj/blob/master/tests/bench/perf.md).