pako

README

Pako

Pako is a scriptable interpreter written in Go.

BEWARE! THIS IS A FORK OF THE ORIGINAL ANKO. THIS WILL BE A DIFFERENT LANGUAGE.

Pako features

• Import directives with local imports. Controlled by Env.Import
• Load function controlled by Env.LoadFrom
• ? operator to handle return values easily.
• as assignments.
• Strict lvalue and rvalue assignment.
• Value unpacking/ignoring. Using ()
• Operator override
• Struct declaration
• Safe and unsafe division of the packages.
• Struct methods
• Struct constructors.
• Runs struct declarations before executing. See this example.

How it works

Source -> Parser -> VM

Usage Example - Embedded

package main

import (
	"errors"
	"fmt"
	"log"
	"reflect"
	"strconv"

	"github.com/dgrr/pako/env"
	"github.com/dgrr/pako/vm"
)

func main() {
	env.Packages["my_pkg"] = map[string]reflect.Value{
		"print": reflect.ValueOf(fmt.Println),
		"getStr": reflect.ValueOf(func(n int64) (string, error) {
			if n < 0 {
				return "", errors.New("Cannot represent negative numbers")
			}
			return strconv.FormatInt(n, 10), nil
		}),
	}
	e := env.NewEnv()

	script := `import my_pkg as pkg
             str = pkg.getStr(20)?
             pkg.print("My string representation:", str)
             pkg.print("Now should panic!!!")
             pkg.getStr(-1)?`

	_, err := vm.Execute(e, nil, script)
	if err != nil {
		log.Fatalf("Execute error: %v\n", err)
	}
	// output:
	// My string representation: 20
	// Now should panic!!!
}

More examples are located in the GoDoc:

https://godoc.org/github.com/dgrr/pako/vm

Usage Example - Command Line

Building

go get github.com/dgrr/pako
go install github.com/dgrr/pako

Running an Pako script file named script.pak

pako script.pak

Pako Script Quick Start

// declare variables
x = 1
y = x + 1

// print using outside the script defined println function
println(x + y) // 3

// if else statement
if x < 1 || y < 1 {
	println(x)
} else if x < 1 && y < 1 {
	println(y)
} else {
	println(x + y)
}

// slice
a = []interface{1, 2, 3}
println(a) // [1 2 3]
println(a[0]) // 1

// map
a = map[interface]interface{"x": 1}
println(a) // map[x:1]
a.b = 2
a["c"] = 3
println(a["b"]) // 2
println(a.c) // 3

// struct
a = make(struct {
	A int64,
	B float64
})
a.A = 4
a.B = 5.5
println(a.A) // 4
println(a.B) // 5.5

// function
fn a (x) {
	println(x + 1)
}
a(5) // 6

Please note that the master branch is not stable

The master branch language and API may change at any time.

To mitigate breaking changes, please use tagged branches. New tagged branches will be created for breaking changes.

Original author

Yasuhiro Matsumoto (a.k.a mattn)

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