415 lines
11 KiB
Markdown
415 lines
11 KiB
Markdown
<p align="center">
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<img src="https://raw.githubusercontent.com/d5/tengolang.com/master/logo_400.png" width="200" height="200">
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</p>
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# The Tengo Language
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[](https://godoc.org/github.com/d5/tengo/script)
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[](https://goreportcard.com/report/github.com/d5/tengo)
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Tengo is an embeddable script language for Go.
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Tengo is [fast](#benchmark) as it's compiled to bytecode and executed on stack-based VM that's written in native Go.
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\>> **Try [Tengo Playground](https://tengolang.com/)** <<
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## Features
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- Simple and intuitive [syntax](https://github.com/d5/tengo#tengo-syntax-in-5-minutes)
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- Dynamically typed with type coercions
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- First-class functions and Closures
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- Garbage collected _(thanks to Go runtime)_
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- Easily extendible using customizable types
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- Written in pure Go _(no CGO, no external dependencies)_
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- Excutable as a [standalone language](https://github.com/d5/tengo#tengo-as-a-standalone-language) _(without writing any Go code)_
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## Benchmark
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| | fib(35) | fibt(35) | Type |
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| :--- | ---: | ---: | :---: |
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| Go | `59ms` | `4ms` | Go (native) |
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| [**Tengo**](https://github.com/d5/tengo) | `4,809ms` | `5ms` | VM on Go |
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| Lua | `1,752ms` | `3ms` | Lua (native) |
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| [go-lua](https://github.com/Shopify/go-lua) | `5,236ms` | `5ms` | Lua VM on Go |
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| [GopherLua](https://github.com/yuin/gopher-lua) | `5,558ms` | `5ms` | Lua VM on Go |
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| Python | `3,132ms` | `28ms` | Python (native) |
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| [otto](https://github.com/robertkrimen/otto) | `85,765ms` | `22ms` | JS Interpreter on Go |
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| [Anko](https://github.com/mattn/anko) | `99,235ms` | `24ms` | Interpreter on Go |
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[fib(35)](https://github.com/d5/tengobench/blob/master/code/fib.tengo) is a function to compute 35th Fibonacci number, and, [fibt(35)](https://github.com/d5/tengobench/blob/master/code/fibtc.tengo) is the [tail-call](https://en.wikipedia.org/wiki/Tail_call) version of the same function. You can see all the code used for this test in [tengobench](https://github.com/d5/tengobench).
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## Tengo Syntax in 5 Minutes
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Tengo supports line comments (`//...`) and block comments (`/* ... */`).
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```golang
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/*
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multi-line block comments
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*/
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a := 5 // line comments
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```
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> [Run in Playground](https://tengolang.com/?s=02e384399a0397b0a752f08604ccb244d1a6cb37)
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Tengo is a dynamically typed language, and, you can initialize the variables using `:=` operator.
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```golang
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a := 1984 // int
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b := "aomame" // string
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c := -9.22 // float
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d := true // bool
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e := '九' // char
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f := [1, false, "foo"] // array
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g := { // map
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h: 439,
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i: 12.34,
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j: [0, 9, false]
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}
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k := func(l, m) { // function
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return l + m
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}
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```
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> [Run in Playground](https://tengolang.com/?s=f8626a711769502ce20e4560ace65c0e9c1279f4)
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After the variable is initialized, it can be re-assigned different value using `=` operator.
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```golang
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a := 1928 // int
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a = "foo" // string
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f := func() {
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a := false // 'a' is defined in the function scope
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a = [1, 2, 3] // and thus does not affect 'a' in global scope.
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}
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a == "foo" // still "foo"
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```
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> [Run in Playground](https://tengolang.com/?s=1d39bc2af5c51417df82b32db47a0e6a156d48ec)
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Type is not directly specified, but, you can use type-coercion functions to convert between types.
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```golang
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s1 := string(1984) // "1984"
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i2 := int("-999") // -999
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f3 := float(-51) // -51.0
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b4 := bool(1) // true
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c5 := char("X") // 'X'
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```
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> [Run in Playground](https://tengolang.com/?s=8d57905b82959eb244e9bbd2111e12ee04a33045)
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_See [Variable Types](https://github.com/d5/tengo/wiki/Variable-Types) for more details on the variable types._
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You can use the dot selector (`.`) and indexer (`[]`) operator to read or write elemens of arrays, strings, or maps.
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```golang
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["one", "two", "three"][1] // == "two"
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m := {
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a: 1,
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b: [2, 3, 4],
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c: func() { return 10 }
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}
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m.a // == 1
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m["b"][1] // == 3
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m.c() // == 10
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m.x = 5 // add 'x' to map 'm'
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//m.b[5] = 0 // but this is an error: index out of bounds
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```
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> [Run in Playground](https://tengolang.com/?s=d510c75ed8f06ef1e22c1aaf8a7d4565c793514c)
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For sequence types (string, bytes, array), you can use slice operator (`[:]`) too.
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```golang
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a := [1, 2, 3, 4, 5][1:3] // == [2, 3]
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b := [1, 2, 3, 4, 5][3:] // == [4, 5]
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c := [1, 2, 3, 4, 5][:3] // == [1, 2, 3]
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d := "hello world"[2:10] // == "llo worl"
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```
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> [Run in Playground](https://tengolang.com/?s=214ab490bb24549578770984985f6b161aed915d)
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In Tengo, functions are first-class citizen, and, it also supports closures, functions that captures variables in outer scopes. In the following example, the function returned from `adder` is capturing `base` variable.
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```golang
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adder := func(base) {
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return func(x) { return base + x } // capturing 'base'
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}
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add5 := adder(5)
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nine := add5(4) // == 9
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```
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> [Run in Playground](https://tengolang.com/?s=fba79990473d5b38cc944dfa225d38580ddaf422)
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For flow control, Tengo currently supports **if-else**, **for**, **for-in** statements.
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```golang
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// IF-ELSE
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if a < 0 {
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// ...
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} else if a == 0 {
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// ...
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} else {
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// ...
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}
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// IF with init statement
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if a := 0; a < 10 {
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// ...
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} else {
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// ...
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}
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// FOR
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for a:=0; a<10; a++ {
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// ...
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}
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// FOR condition-only (like WHILE in other languages)
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for a < 10 {
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// ...
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}
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// FOR-IN
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for x in [1, 2, 3] { // array: element
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// ...
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}
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for i, x in [1, 2, 3] { // array: index and element
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// ...
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}
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for k, v in {k1: 1, k2: 2} { // map: key and value
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// ...
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}
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```
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An error object is created using `error` function-like keyword. An error can have any types of value and the underlying value of the error can be accessed using `.value` selector.
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```golang
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err1 := error("oops") // error with string value
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err2 := error(1+2+3) // error with int value
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if is_error(err1) { // 'is_error' builtin function
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err_val := err1.value // get underlying value
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}
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```
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> [Run in Playground](https://tengolang.com/?s=5eaba4289c9d284d97704dd09cb15f4f03ad05c1)
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You can load other scripts as modules using `import` expression.
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Main script:
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```golang
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mod1 := import("./mod1") // assuming mod1.tengo file exists in the current directory
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// same as 'import("./mod1.tengo")' or 'import("mod1")'
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mod1.func1(a) // module function
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a += mod1.foo // module variable
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//mod1.foo = 5 // error: module variables are read-only
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```
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`mod1.tengo` file:
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```golang
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func1 := func(x) { print(x) }
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foo := 2
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```
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Basically `import` expression returns all the global variables defined in the module as a Map-like value. One can access the functions or variables defined in the module using `.` selector or `["key"]` indexer, but, module variables are immutable.
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## Embedding Tengo in Go
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To execute Tengo code in your Go codebase, you should use **Script**. In the simple use cases, all you need is to do is to create a new Script instance and call its `Script.Run()` function.
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```golang
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import "github.com/d5/tengo/script"
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var code = `
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reduce := func(seq, fn) {
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s := 0
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for x in seq { fn(x, s) }
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return s
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}
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print(reduce([1, 2, 3], func(x, s) { s += x }))
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`
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func main() {
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s := script.New([]byte(code))
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if _, err := s.Run(); err != nil {
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panic(err)
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}
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}
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```
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If you want to compile the source script once and execute it multiple times, you can use `Script.Compile()` function that returns **Compiled** instance.
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```golang
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import (
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"fmt"
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"github.com/d5/tengo/script"
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)
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func main() {
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s := script.New([]byte(`a := b + 20`))
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// define variable 'b'
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_ = s.Add("b", 10)
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// compile the source
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c, err := s.Compile()
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if err != nil {
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panic(err)
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}
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// run the compiled bytecode
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// a compiled bytecode 'c' can be executed multiple without re-compiling it
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if err := c.Run(); err != nil {
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panic(err)
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}
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// retrieve value of 'a'
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a := c.Get("a")
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fmt.Println(a.Int())
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}
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```
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In the example above, a variable `b` is defined by the user before compiliation using `Script.Add()` function. Then a compiled bytecode `c` is used to execute the bytecode and get the value of global variables. In this example, the value of global variable `a` is read using `Compiled.Get()` function.
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If you need the custom data types (outside Tengo's primitive types), you can define your own `struct` that implements `objects.Object` interface _(and optionally `objects.Callable` if you want to make function-like invokable objects)_.
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```golang
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import (
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"errors"
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"fmt"
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"github.com/d5/tengo/compiler/token"
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"github.com/d5/tengo/objects"
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"github.com/d5/tengo/script"
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)
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type Counter struct {
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value int64
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}
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func (o *Counter) TypeName() string {
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return "counter"
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}
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func (o *Counter) String() string {
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return fmt.Sprintf("Counter(%d)", o.value)
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}
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func (o *Counter) BinaryOp(op token.Token, rhs objects.Object) (objects.Object, error) {
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switch rhs := rhs.(type) {
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case *Counter:
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switch op {
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case token.Add:
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return &Counter{value: o.value + rhs.value}, nil
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case token.Sub:
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return &Counter{value: o.value - rhs.value}, nil
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}
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case *objects.Int:
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switch op {
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case token.Add:
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return &Counter{value: o.value + rhs.Value}, nil
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case token.Sub:
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return &Counter{value: o.value - rhs.Value}, nil
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}
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}
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return nil, errors.New("invalid operator")
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}
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func (o *Counter) IsFalsy() bool {
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return o.value == 0
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}
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func (o *Counter) Equals(t objects.Object) bool {
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if tc, ok := t.(*Counter); ok {
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return o.value == tc.value
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}
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return false
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}
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func (o *Counter) Copy() objects.Object {
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return &Counter{value: o.value}
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}
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func (o *Counter) Call(args ...objects.Object) (objects.Object, error) {
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return &objects.Int{Value: o.value}, nil
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}
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var code = []byte(`
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arr := [1, 2, 3, 4]
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for x in arr {
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c1 += x
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}
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out := c1()`)
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func main() {
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s := script.New(code)
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// define variable 'c1'
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_ = s.Add("c1", &Counter{value: 5})
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// compile the source
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c, err := s.Run()
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if err != nil {
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panic(err)
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}
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// retrieve value of 'out'
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out := c.Get("out")
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fmt.Println(out.Int()) // prints "15" ( = 5 + (1 + 2 + 3 + 4) )
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}
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```
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As an alternative to using **Script**, you can directly create and interact with the parser, compiler and VMs directly. There's no good documentations yet, but, check out Script code if you are interested.
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## Tengo as a Standalone Language
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Although Tengo is designed as an embedded script language for Go, it can be compiled and executed as native binary without any Go code using `tengo` tool.
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### Installing Tengo Tool
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To install `tengo` tool, run:
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```bash
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go get github.com/d5/tengo/cmd/tengo
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```
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### Compiling and Executing Tengo Code
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You can directly execute the Tengo source code by running `tengo` tool with your Tengo source file (`*.tengo`).
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```bash
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tengo myapp.tengo
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```
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Or, you can compile the code into a binary file and execute it later.
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```bash
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tengo -c -o myapp myapp.tengo # compile 'myapp.tengo' into binary file 'myapp'
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tengo myapp # execute the compiled binary `myapp`
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```
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### Tengo REPL
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You can run Tengo [REPL](https://en.wikipedia.org/wiki/Read–eval–print_loop) if you run `tengo` with no arguments.
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```bash
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tengo
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```
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## Roadmap
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Development roadmap for Tengo:
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- Standard libraries _(modules)_
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- Better documentations
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- More language constructs such as destructuring assignment, `this` binding for object methods, switch-case statements
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- Native executables compilation
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- Performance improvements
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- Syntax highlighter for IDEs
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