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goplus / xgo deb

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xgo / usr / lib / xgo / doc / docs.md
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XGo Quick Start

XGo is the first AI-native programming language that integrates software engineering into a unified whole.

XGo := C * Go * Python * JavaScript + Scratch

Our vision is to enable everyone to become a builder of the world.

Easy to learn

  • Simple and easy to understand
  • Smaller syntax set than Go and Python in best practices

Ready for large projects

  • Integrate C/C++, Go, Python, and JavaScript into a unified ecosystem
  • Derived from Go and easy to build large projects from its good engineering foundation

The XGo programming language is designed for engineering, STEM education, and data science.

  • For engineering: working in the simplest language that can be mastered by children.
  • For STEM education: studying an engineering language that can be used for work in the future.
  • For data science: communicating with engineers in the same language.

How to install

Note: Requires go1.19 or later

on Windows

winget install goplus.xgo

on Debian/Ubuntu

sudo bash -c ' echo "deb [trusted=yes] https://pkgs.xgo.dev/apt/ /" > /etc/apt/sources.list.d/goplus.list'
sudo apt update
sudo apt install xgo

on RedHat/CentOS/Fedora

sudo bash -c 'echo -e "[goplus]\nname=XGo Repo\nbaseurl=https://pkgs.xgo.dev/yum/\nenabled=1\ngpgcheck=0" > /etc/yum.repos.d/goplus.repo'
sudo yum install xgo

on macOS/Linux (Homebrew)

Install via brew

$ brew install xgo

from source code

git clone https://github.com/goplus/xgo.git
cd xgo

# On mac/linux run:
./all.bash
# On Windows run:
all.bat

Actually, all.bash and all.bat will use go run cmd/make.go underneath.

Running in XGo playground

If you don't want install XGo, you can write your XGo programs in XGo playground. This is the fastest way to experience XGo.

And you can share your XGo code with your friends. Here is my Hello world program:

Table of Contents

Hello World

Different from the function call style of most languages, XGo recommends command style code:

println "Hello world"

Save this snippet into a file named hello.xgo. Now do: xgo run hello.xgo.

Congratulations - you just wrote and executed your first XGo program!

You can compile a program without execution with xgo build hello.xgo. See xgo help for all supported commands.

println is one of the few built-in functions. It prints the value passed to it to standard output.

To emphasize our preference for command style, we introduce echo as an alias for println:

echo "Hello world"

See https://tutorial.xgo.dev/hello-world for more details.

Running a project folder with several files

Suppose you have a folder with several .xgo files in it, and you want to compile them all into one program. Just do: xgo run ..

Passing parameters also works, so you can do: xgo run . --yourparams some_other_stuff.

Your program can then use the CLI parameters like this:

import "os"

echo os.Args

Comments

# This is a single line comment.

// This is a single line comment.

/*
This is a multiline comment.
*/

Variables

name := "Bob"
age := 20
largeNumber := int128(1 << 65)
echo name, age
echo largeNumber

Variables are declared and initialized with :=.

The variable's type is inferred from the value on the right hand side. To choose a different type, use type conversion: the expression T(v) converts the value v to the type T.

Initialization vs. assignment

Note the (important) difference between := and =. := is used for declaring and initializing, = is used for assigning.

age = 21

This code will not compile, because the variable age is not declared. All variables need to be declared in XGo.

age := 21

The values of multiple variables can be changed in one line. In this way, their values can be swapped without an intermediary variable.

a, b := 0, 1
a, b = b, a
echo a, b // 1, 0

XGo Types

Primitive types

bool

int8    int16   int32   int    int64    int128
uint8   uint16  uint32  uint   uint64   uint128

uintptr // similar to C's size_t

byte // alias for uint8
rune // alias for int32, represents a Unicode code point

string

float32 float64

complex64 complex128

bigint bigrat

unsafe.Pointer // similar to C's void*

any // alias for Go's interface{}

Strings

name := "Bob"
echo name.len  // 3
echo name[0]   // 66
echo name[1:3] // ob
echo name[:2]  // Bo
echo name[2:]  // b

// or using octal escape `\###` notation where `#` is an octal digit
echo "\141a"   // aa

// Unicode can be specified directly as `\u####` where # is a hex digit
// and will be converted internally to its UTF-8 representation
echo "\u2605"  // ★

String values are immutable. You cannot mutate elements:

s := "hello 🌎"
s[0] = `H` // not allowed

Note that indexing a string will produce a byte, not a rune nor another string.

Strings can be easily converted to integers:

s := "12"
a, err := s.int
b := s.int! // will panic if s isn't a valid integer

String operators

name := "Bob"
bobby := name + "by" // + is used to concatenate strings
echo bobby // Bobby

s := "Hello "
s += "world"
echo s // Hello world

Most XGo operators must have values of the same type on both sides. You cannot concatenate an integer to a string:

age := 10
echo "age = " + age // not allowed

We have to either convert age to a string:

age := 10
echo "age = " + age.string

However, you can replace age.string to "${age}":

age := 10
echo "age = ${age}"

Here is a more complex example of ${expr}:

host := "example.com"
page := 0
limit := 20
echo "https://${host}/items?page=${page+1}&limit=${limit}" // https://example.com/items?page=1&limit=20
echo "$$" // $

Runes

A rune represents a single Unicode character and is an alias for int32.

rocket := '🚀'
echo rocket         // 128640
echo string(rocket) // 🚀

Numbers

a := 123

This will assign the value of 123 to a. By default a will have the type int.

You can also use hexadecimal, binary or octal notation for integer literals:

a := 0x7B
b := 0b01111011
c := 0o173

All of these will be assigned the same value, 123. They will all have type int, no matter what notation you used.

XGo also supports writing numbers with _ as separator:

num := 1_000_000 // same as 1000000

If you want a different type of integer, you can use casting:

a := int64(123)
b := uint8(12)
c := int128(12345)

Assigning floating point numbers works the same way:

f1 := 1.0
f2 := float32(3.14)

If you do not specify the type explicitly, by default float literals will have the type of float64.

Float literals can also be declared as a power of ten:

f0 := 42e1   // 420
f1 := 123e-2 // 1.23
f2 := 456e+2 // 45600

XGo has built-in support for rational numbers:

a := 1r << 200  // suffix `r` means `rational`
b := bigint(1 << 200)

And you can cast bool to number types (this is NOT supported in Go):

echo int(true)       // 1
echo float64(true)   // 1
echo complex64(true) // (1+0i)

Slices

A slice is a collection of data elements of the same type. A slice literal is a list of expressions surrounded by square brackets. An individual element can be accessed using an index expression. Indexes start from 0:

nums := [1, 2, 3]
echo nums      // [1 2 3]
echo nums.len  // 3
echo nums[0]   // 1
echo nums[1:3] // [2 3]
echo nums[:2]  // [1 2]
echo nums[2:]  // [3]

nums[1] = 5
echo nums // [1 5 3]

Type of a slice literal is infered automatically.

a := [1, 2, 3]   // []int
b := [1, 2, 3.4] // []float64
c := ["Hi"]      // []string
d := ["Hi", 10]  // []any
d := []          // []any

And casting slice literals also works.

a := []float64([1, 2, 3]) // []float64

Appending to slices

XGo provides a convenient <- operator for appending elements to slices, which is more intuitive than Go's append function:

a := [1, 2, 3]
a <- 4           // append single element
a <- 5, 6, 7     // append multiple elements
b := [8, 9]
a <- b...        // append another slice

echo a // [1 2 3 4 5 6 7 8 9]

This is equivalent to Go's append operations:

  • a <- v is the same as a = append(a, v)
  • a <- v1, v2, v3 is the same as a = append(a, v1, v2, v3)
  • a <- b... is the same as a = append(a, b...)

Maps

A map literal is a list of expressions surrounded by curly braces.

a := {"Hello": 1, "xsw": 3}     // map[string]int
b := {"Hello": 1, "xsw": 3.4}   // map[string]float64
c := {"Hello": 1, "xsw": "XGo"} // map[string]any
e := {1: "one", 2: "two"}       // map[int]string
d := {}                         // map[string]any

Use make for empty maps or to pre-allocate capacity for better performance.

m := make(map[string]int)          // Basic creation
large := make(map[string]int, 100) // Pre-allocated for ~100 elements

Before manipulating maps, it is important to understand that XGo supports two notations for referencing keys:

  • Bracket Notation (m["key"]): The universal syntax. It works for all key types and allows using variables as keys.
  • Field Access Notation (m.key): A convenient shorthand for string-keyed maps when the key is a valid identifier (no spaces or special characters).

Field access is pure syntax sugar - m.field and m["field"] behave identically in all contexts.

Both notations are used for both assigning values and retrieving them.

Adding and Updating Elements

a := {"a": 1, "b": 0}

// Using bracket notation
a["c"] = 100

// Using field notation
a.d = 200

echo a  // Output: map[a:1 b:0 c:100 d:200]

// Works with maps created by make too
m := make(map[string]int)
m["x"] = 10
m.y = 20
echo m  // Output: map[x:10 y:20]

Deleting Elements

Use the delete function to remove elements from a map:

a := {"a": 1, "b": 0, "c": 100}
delete(a, "b")
echo a  // Output: map[a:1 c:100]

Getting Map Length

You can get the number of elements in a map using the len function:

a := {"a": 1, "b": 2, "c": 3}
echo len(a)  // Output: 3

Accessing Elements

config := {"host": "localhost", "port": 8080}
echo config.host  // Output: localhost
echo config.port  // Output: 8080

// Equivalent to:
echo config["host"]
echo config["port"]
Working with any Type

Either notation also works with variables of type any, automatically treating them as map[string]any:

var response any = {"status": "ok", "code": 200}
echo response.status  // Output: ok
echo response.code    // Output: 200
Safe Access with Comma-ok

When accessing uncertain data (such as from JSON or external APIs), use the comma-ok form to safely check if a path exists. The comma-ok form returns two values:

  • The value itself (or zero value if path doesn't exist)
  • A boolean indicating whether the access succeeded

With comma-ok, accessing non-existent paths never panics - it simply returns false:

var data any = fetchFromAPI()

// Without comma-ok - may panic if structure is wrong
// name := data.user.profile.name.(string)

// With comma-ok - safe, never panics
name, ok := data.user.profile.name.(string)
if ok {
    // ...
}

Module imports

For information about creating a module, see Modules.

Modules can be imported using the import keyword:

import "strings"

x := strings.NewReplacer("?", "!").Replace("Hello, world???")
echo x // Hello, world!!!

Module import aliasing

Any imported module name can be aliased:

import strop "strings"

x := strop.NewReplacer("?", "!").Replace("Hello, world???")
echo x // Hello, world!!!

Statements & expressions

If..else

In XGo, if statements are pretty straightforward and similar to most other languages. Unlike other C-like languages, there are no parentheses surrounding the condition and the braces are always required.

a := 10
b := 20
if a < b {
    echo "a < b"
} else if a > b {
    echo "a > b"
} else {
    echo "a == b"
}

For loop

XGo has only one looping keyword: for, with several forms.

for..in

This is the most common form. You can use it with a slice, map, numeric range or custom iterators.

For information about creating a custom iterators, see Custom iterators.

Slice for

The for value in arr form is used for going through elements of a slice.

numbers := [1, 3, 5, 7, 11, 13, 17]
sum := 0
for x in numbers {
    sum += x
}
echo sum // 57

If an index is required, an alternative form for index, value in arr can be used.

names := ["Sam", "Peter"]
for i, name in names {
    echo i, name
    // 0 Sam
    // 1 Peter
}
Map for
m := {"one": 1, "two": 2}
for key, val in m {
    echo key, val
    // one 1
    // two 2
}
for key, _ in m {
    echo key
    // one
    // two
}
for val in m {
    echo val
    // 1
    // 2
}
Range for

You can use range expression (start:end:step) in for loop.

for i in :5 {
    echo i
    // 0
    // 1
    // 2
    // 3
    // 4
}
for i in 1:5 {
    echo i
    // 1
    // 2
    // 3
    // 4
}
for i in 1:5:2 {
    echo i
    // 1
    // 3
}
for/in/if

All loops of for/in form can have an optional if condition.

numbers := [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
for num in numbers if num%3 == 0 {
    echo num
    // 0
    // 3
    // 6
    // 9
}

for num in :10 if num%3 == 0 {
    echo num
    // 0
    // 3
    // 6
    // 9
}

Condition for

sum := 0
i := 1
for i <= 100 {
    sum += i
    i++
}
echo sum // 5050

This form of the loop is similar to while loops in other languages. The loop will stop iterating once the boolean condition evaluates to false. Again, there are no parentheses surrounding the condition, and the braces are always required.

C for

for i := 0; i < 10; i += 2 {
    // Don't print 6
    if i == 6 {
        continue
    }
    echo i
    // 0
    // 2
    // 4
    // 8
}

Finally, there's the traditional C style for loop. It's safer than the while form because with the latter it's easy to forget to update the counter and get stuck in an infinite loop.

Bare for

for {
    // ...
}

The condition can be omitted, resulting in an infinite loop. You can use break or return to end the loop.

Error handling

We reinvent the error handling specification in XGo. We call them ErrWrap expressions:

expr! // panic if err
expr? // return if err
expr?:defval // use defval if err

How to use them? Here is an example:

import (
    "strconv"
)

func add(x, y string) (int, error) {
    return strconv.Atoi(x)? + strconv.Atoi(y)?, nil
}

func addSafe(x, y string) int {
    return strconv.Atoi(x)?:0 + strconv.Atoi(y)?:0
}

echo `add("100", "23"):`, add("100", "23")!

sum, err := add("10", "abc")
echo `add("10", "abc"):`, sum, err

echo `addSafe("10", "abc"):`, addSafe("10", "abc")

The output of this example is:

add("100", "23"): 123
add("10", "abc"): 0 strconv.Atoi: parsing "abc": invalid syntax

===> errors stack:
main.add("10", "abc")
    /Users/xsw/tutorial/15-ErrWrap/err_wrap.xgo:6 strconv.Atoi(y)?

addSafe("10", "abc"): 10

Compared to corresponding Go code, It is clear and more readable.

And the most interesting thing is, the return error contains the full error stack. When we got an error, it is very easy to position what the root cause is.

How these ErrWrap expressions work? See Error Handling for more information.

Functions

func add(x int, y int) int {
    return x + y
}

echo add(2, 3) // 5

Returning multiple values

func foo() (int, int) {
    return 2, 3
}

a, b := foo()
echo a // 2
echo b // 3
c, _ := foo() // ignore values using `_`

Optional parameters

XGo supports optional parameters using the T? syntax. Optional parameters must have zero values as their defaults.

func greet(name string, count int?) {
    if count == 0 {
        count = 1
    }
    for i := 0; i < count; i++ {
        echo "Hello,", name
    }
}

greet "Alice", 3  // prints "Hello, Alice" three times
greet "Bob"       // prints "Hello, Bob" once (default behavior)

Optional parameters are denoted by adding ? after the parameter type. The default value is always the zero value of that type (e.g., 0 for integers, "" for strings, false for booleans).

func connect(host string, port int?, secure bool?) {
    if port == 0 {
        port = 80
    }
    echo "Connecting to", host, "on port", port, "secure:", secure
}

connect "example.com", 443, true  // Connecting to example.com on port 443 secure: true
connect "example.com"             // Connecting to example.com on port 80 secure: false

Variadic parameters

func sum(a ...int) int {
    total := 0
    for x in a {
        total += x
    }
    return total
}

echo sum(2, 3, 5) // 10

Output parameters can have names.

func sum(a ...int) (total int) {
    for x in a {
        total += x
    }
    return // don't need return values if they are assigned
}

echo sum(2, 3, 5) // 10

Keyword arguments

XGo supports Python-like keyword arguments (kwargs) syntax for improved code readability. When calling functions with many parameters, you can use key=value syntax to make your code more expressive and command-line-style.

Using kwargs with maps

func process(opts map[string]any?, args ...any) {
    if name, ok := opts["name"]; ok {
        echo "Name:", name
    }
    if age, ok := opts["age"]; ok {
        echo "Age:", age
    }
    echo "Args:", args
}

process name = "Ken", age = 17              // keyword parameters only
process "extra", 1, name = "Ken", age = 17  // variadic parameters first, then keyword parameters
process                                     // all parameters optional

Using kwargs with structs

You can also use structs or struct pointers for keyword parameters, which provides type safety:

type Config struct {
    Timeout    int
    MaxRetries int
    Debug      bool
}

func run(cfg *Config?) {
    timeout := 30
    maxRetries := 3
    debug := false
    if cfg != nil {
        if cfg.Timeout > 0 {
            timeout = cfg.Timeout
        }
        if cfg.MaxRetries > 0 {
            maxRetries = cfg.MaxRetries
        }
        debug = cfg.Debug
    }
    echo "Timeout:", timeout, "MaxRetries:", maxRetries, "Debug:", debug
}

run timeout = 60, maxRetries = 5           // lowercase field names work
run Timeout = 10, Debug = true             // uppercase field names work too
run                                        // uses default values

Key rules:

  • The keyword parameter must be an optional parameter.
  • The keyword parameter must be the last parameter (without variadic) or second-to-last (with variadic).
  • When calling a function, keyword arguments must be placed after all normal parameters (including variadic parameters). This might seem inconsistent with the order of keyword and variadic parameters in a function declaration, but that's the rule.

Higher order functions

Functions can also be parameters.

func square(x float64) float64 {
    return x*x
}

func abs(x float64) float64 {
    if x < 0 {
        return -x
    }
    return x
}

func transform(a []float64, f func(float64) float64) []float64 {
    return [f(x) for x in a]
}

y := transform([1, 2, 3], square)
echo y // [1 4 9]

z := transform([-3, 1, -5], abs)
echo z // [3 1 5]

Lambda expressions

You also can use lambda expression to define a anonymous function.

func transform(a []float64, f func(float64) float64) []float64 {
    return [f(x) for x in a]
}

y := transform([1, 2, 3], x => x*x)
echo y // [1 4 9]

z := transform([-3, 1, -5], x => {
    if x < 0 {
        return -x
    }
    return x
})
echo z // [3 1 5]

Structs

Struct tags

Go does not provide a way to add reflection information to a struct type. XGo uses Go's built-in struct field tags to implement struct type tags. For example:

type Start struct {
    _ "Start recording meeting minutes"
}

It is equivalent to

type Start struct {
    _ struct{} `_:"Start recording meeting minutes"`
}

Custom iterators

For range of UDT

type Foo struct {
}

// Gop_Enum(proc func(val ValType)) or:
// Gop_Enum(proc func(key KeyType, val ValType))
func (p *Foo) Gop_Enum(proc func(key int, val string)) {
    // ...
}

foo := &Foo{}
for k, v := range foo {
    echo k, v
}

for k, v in foo {
    echo k, v
}

echo {v: k for k, v in foo}

Note: you can't use break/continue or return statements in for range of udt.Gop_Enum(callback).

For range of UDT2

type FooIter struct {
}

// (Iterator) Next() (val ValType, ok bool) or:
// (Iterator) Next() (key KeyType, val ValType, ok bool)
func (p *FooIter) Next() (key int, val string, ok bool) {
    // ...
}

type Foo struct {
}

// Gop_Enum() Iterator
func (p *Foo) Gop_Enum() *FooIter {
    // ...
}

foo := &Foo{}
for k, v := range foo {
    echo k, v
}

for k, v in foo {
    echo k, v
}

echo {v: k for k, v in foo}

Deduce struct type

type Config struct {
    Dir   string
    Level int
}

func foo(conf *Config) {
    // ...
}

foo {Dir: "/foo/bar", Level: 1}

Here foo {Dir: "/foo/bar", Level: 1} is equivalent to foo(&Config{Dir: "/foo/bar", Level: 1}). However, you can't replace foo(&Config{"/foo/bar", 1}) with foo {"/foo/bar", 1}, because it is confusing to consider {"/foo/bar", 1} as a struct literal.

You also can omit struct types in a return statement. For example:

type Result struct {
    Text string
}

func foo() *Result {
    return {Text: "Hi, XGo"} // return &Result{Text: "Hi, XGo"}
}

Overload operators

import "math/big"

type MyBigInt struct {
    *big.Int
}

func Int(v *big.Int) MyBigInt {
    return MyBigInt{v}
}

func (a MyBigInt) + (b MyBigInt) MyBigInt { // binary operator
    return MyBigInt{new(big.Int).Add(a.Int, b.Int)}
}

func (a MyBigInt) += (b MyBigInt) {
    a.Int.Add(a.Int, b.Int)
}

func -(a MyBigInt) MyBigInt { // unary operator
    return MyBigInt{new(big.Int).Neg(a.Int)}
}

a := Int(1r)
a += Int(2r)
echo a + Int(3r)
echo -a

Auto property

Let's see an example written in XGo:

import "xgo/ast/goptest"

doc := goptest.New(`... XGo code ...`)!

echo doc.Any().FuncDecl().Name()

In many languages, there is a concept named property who has get and set methods.

Suppose we have get property, the above example will be:

import "xgo/ast/goptest"

doc := goptest.New(`... XGo code ...`)!

echo doc.any.funcDecl.name

In XGo, we introduce a concept named auto property. It is a get property, but is implemented automatically. If we have a method named Bar(), then we will have a get property named bar at the same time.

Go/XGo hybrid programming

This is an example to show how to mix Go/XGo code in the same package.

In this example, we have a Go source file named a.go:

package main

import "fmt"

func p(a interface{}) {
    sayMix()
    fmt.Println("Hello,", a)
}

And we have an XGo source file named b.xgo:

func sayMix() {
    echo "Mix Go and XGo"
}

p "world"

You can see that Go calls an XGo function named sayMix, and XGo calls a Go function named p. As you are used to in Go programming, this kind of circular reference is allowed.

Run xgo run . to see the output of this example:

Mix Go and XGo
Hello, world

Run XGo in watch mode

The xgo command can run in watch mode so that everytime an XGo file is changed it is transpiled to a Go file:

xgo watch [-gentest] [dir]

By default xgo watch does not convert test files (normally ending with _test.xgo). You can specify -gentest flag to force converting all XGo files.

Calling C from XGo

Here is an example to show how XGo interacts with C.

import "c"

c.printf c"Hello, llgo!\n"
c.fprintf c.Stderr, c"Hi, %6.1f\n", 3.14

Here import "c" is used to import libc. In this example we call two C standard functions printf and fprintf, passing a C variable stderr and two C strings in the form of c"xxx" (an XGo syntax to represent C-style strings).

To run this demo, you need to set the XGO_GOCMD environment variable first.

export XGO_GOCMD=llgo  # default is `go`

Then execute xgo run . to see the output of this example:

Hello, llgo!
Hi,    3.1

Data processing

Rational numbers

We introduce rational numbers as primitive XGo types. We use suffix r to denote rational literals. For example, 1r << 200 means a big int whose value is equal to 2200.

a := 1r << 200
b := bigint(1 << 200)

By default, 1r will have the type of bigint.

And 4/5r means the rational constant 4/5. It will have the type of bigrat.

a := 4/5r
b := a - 1/3r + 3 * 1/2r
echo a, b // 4/5 59/30

Casting rational numbers works like other primitive types:

a := 1r
b := bigrat(1r)
c := bigrat(1)
echo a/3 // 0
echo b/3 // 1/3
echo c/3 // 1/3

List comprehension

a := [x*x for x in [1, 3, 5, 7, 11]]
b := [x*x for x in [1, 3, 5, 7, 11] if x > 3]
c := [i+v for i, v in [1, 3, 5, 7, 11] if i%2 == 1]

arr := [1, 2, 3, 4, 5, 6]
d := [[a, b] for a in arr if a < b for b in arr if b > 2]

x := {x: i for i, x in [1, 3, 5, 7, 11]}
y := {x: i for i, x in [1, 3, 5, 7, 11] if i%2 == 1}
z := {v: k for k, v in {1: "Hello", 3: "Hi", 5: "xsw", 7: "XGo"} if k > 3}

Select data from a collection

type student struct {
    name  string
    score int
}

students := [student{"Ken", 90}, student{"Jason", 80}, student{"Lily", 85}]

unknownScore, ok := {x.score for x in students if x.name == "Unknown"}
jasonScore := {x.score for x in students if x.name == "Jason"}

echo unknownScore, ok // 0 false
echo jasonScore // 80

Check if data exists in a collection

type student struct {
    name  string
    score int
}

students := [student{"Ken", 90}, student{"Jason", 80}, student{"Lily", 85}]

hasJason := {for x in students if x.name == "Jason"} // is any student named Jason?
hasFailed := {for x in students if x.score < 60}     // is any student failed?

Domain-Specific Text Literals

Domain-specific text literals allow you to write inline code in specialized formats—such as JSON, XML, regular expressions, or custom DSLs—without sacrificing the benefits of compile-time checking and editor support.

Basic syntax:

result := domainTag`content`

With parameters:

result := domainTag`> param1, param2
content
`

The ! suffix forces error handling, causing a panic if parsing fails—useful for literals you expect to always be valid.

Built-in Formats

XGo currently supports several domain text literals natively:

Text Processing Language (tpl)

A grammar-based alternative to regular expressions that emphasizes clarity and composability. Ideal for defining parsers and text processors.

grammar := tpl`
expr = term % ("+" | "-")
term = INT % ("*" | "/")
`!

result := grammar.parseExpr("10+5*2", nil)
echo result

Learn more in the TPL documentation.

JSON

Parse and validate JSON structures inline:

config := json`{
	"server": "localhost",
	"port": 8080,
	"features": ["auth", "logging"]
}`!

echo config.port

XML

Work with XML documents directly:

doc := xml`
<configuration>
	<database>
		<host>localhost</host>
		<port>5432</port>
	</database>
</configuration>
`!

CSV

Define tabular data inline:

data := csv`
name,age,city
Alice,30,NYC
Bob,25,SF
`!

HTML

Embed HTML with proper parsing (requires golang.org/x/net/html):

import "golang.org/x/net/html"

page := html`
<html>
	<body>
		<h1>Welcome</h1>
		<p>Domain-specific literals in action</p>
	</body>
</html>
`!

Regular Expressions

Define regex patterns with improved readability. XGo supports both standard and POSIX regex:

pattern := regexp`^[a-z]+\[[0-9]+\]$`!

if pattern.matchString("item[42]") {
	echo "Match found"
}

// POSIX variant
posixPattern := regexposix`[[:alpha:]]+`!

Implementation Details

Domain text literals compile to function calls to the corresponding package's New() function. For example:

json`{"key": "value"}`
// Compiles to:
json.New(`{"key": "value"}`)

This design keeps the feature simple while allowing seamless integration with existing Go packages. The domainTag represents a package that must have a global func New(string) function with any return type.

Unix shebang

You can use XGo programs as shell scripts now. For example:

#!/usr/bin/env -S xgo run

echo "Hello, XGo"

echo 1r << 129
echo 1/3r + 2/7r*2

arr := [1, 3, 5, 7, 11, 13, 17, 19]
echo arr
echo [x*x for x in arr, x > 3]

m := {"Hi": 1, "XGo": 2}
echo m
echo {v: k for k, v in m}
echo [k for k, _ in m]
echo [v for v in m]

Compatibility with Go

All Go features will be supported (including partially support cgo, see below).

All Go packages (even these packages use cgo) can be imported by XGo.

import (
    "fmt"
    "strings"
)

x := strings.NewReplacer("?", "!").Replace("hello, world???")
fmt.Println "x:", x

And all XGo packages can also be imported in Go programs. What you need to do is just using xgo command instead of go.

First, let's make a directory named 14-Using-goplus-in-Go.

Then write an XGo package named foo in it:

package foo

func ReverseMap(m map[string]int) map[int]string {
    return {v: k for k, v in m}
}

Then use it in a Go package 14-Using-goplus-in-Go/gomain:

package main

import (
    "fmt"

    "github.com/goplus/tutorial/14-Using-goplus-in-Go/foo"
)

func main() {
    rmap := foo.ReverseMap(map[string]int{"Hi": 1, "Hello": 2})
    fmt.Println(rmap)
}

How to build this example? You can use:

xgo install -v ./...

Go github.com/goplus/tutorial/14-Using-goplus-in-Go to get the source code.

Bytecode vs. Go code

XGo supports bytecode backend and Go code generation.

When we use xgo command, it generates Go code to covert XGo package into Go packages.

xgo run     # Run an XGo program
xgo install # Build XGo files and install target to GOBIN
xgo build   # Build XGo files
xgo test    # Test XGo packages
xgo fmt     # Format XGo packages
xgo clean   # Clean all XGo auto generated files
xgo go      # Convert XGo packages into Go packages

When we use ixgo command, it interprets and executes the program.

ixgo # Run an XGo program

In bytecode mode, XGo doesn't support cgo. However, in Go-code-generation mode, XGo fully supports cgo.

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