interp

Overview ¶

Package interp provides a complete Go interpreter.

For the Go language itself, refer to the official Go specification https://golang.org/ref/spec.

Importing packages ¶

Packages can be imported in source or binary form, using the standard Go import statement. In source form, packages are searched first in the vendor directory, the preferred way to store source dependencies. If not found in vendor, sources modules will be searched in GOPATH. Go modules are not supported yet by yaegi.

Binary form packages are compiled and linked with the interpreter executable, and exposed to scripts with the Use method. The goexports command can be used to generate package wrappers.

Custom build tags ¶

Custom build tags allow to control which files in imported source packages are interpreted, in the same way as the "-tags" option of the "go build" command. Setting a custom build tag spans globally for all future imports of the session.

A build tag is a line comment that begins

// yaegi:tags

that lists the build constraints to be satisfied by the further imports of source packages.

For example the following custom build tag

// yaegi:tags noasm

Will ensure that an import of a package will exclude files containing

// +build !noasm

And include files containing

// +build noasm

package main

import (
	"fmt"
	"log"

	"github.com/containous/yaegi/interp"
)

func main() {
	// Create a new interpreter context
	i := interp.New(interp.Options{})

	// Run some code: define a new function
	_, err := i.Eval("func f(i int) int { return 2 * i }")
	if err != nil {
		log.Fatal(err)
	}

	// Access the interpreted f function with Eval
	v, err := i.Eval("f")
	if err != nil {
		log.Fatal(err)
	}

	// Returned v is a reflect.Value, so we can use its interface
	f, ok := v.Interface().(func(int) int)
	if !ok {
		log.Fatal("type assertion failed")
	}

	// Use interpreted f as it was pre-compiled
	fmt.Println(f(2))

}

Output:

4