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package expr
	"github.com/antonmedv/expr/checker"
	"github.com/antonmedv/expr/compiler"
	"github.com/antonmedv/expr/internal/conf"
	"github.com/antonmedv/expr/optimizer"
	"github.com/antonmedv/expr/parser"
	"github.com/antonmedv/expr/vm"
// Option for configuring config.
type Option func(c *conf.Config)
// Eval parses, compiles and runs given input.
func Eval(input string, env interface{}) (interface{}, error) {
	if _, ok := env.(Option); ok {
		return nil, fmt.Errorf("misused expr.Eval: second argument (env) should be passed without expr.Env")
	tree, err := parser.Parse(input)
	if err != nil {
		return nil, err
	program, err := compiler.Compile(tree, nil)
	if err != nil {
		return nil, err
	output, err := vm.Run(program, env)
	if err != nil {
		return nil, err
	return output, nil
// Env specifies expected input of env for type checks.
// If struct is passed, all fields will be treated as variables,
// as well as all fields of embedded structs and struct itself.
// If map is passed, all items will be treated as variables.
// Methods defined on this type will be available as functions.
func Env(i interface{}) Option {
	return func(c *conf.Config) {
		if _, ok := i.(map[string]interface{}); ok {
			c.MapEnv = true
		c.Types = conf.CreateTypesTable(i)
// Operator allows to override binary operator with function.
func Operator(operator string, fn ...string) Option {
	return func(c *conf.Config) {
		c.Operators[operator] = append(c.Operators[operator], fn...)
// AsBool tells the compiler to expect boolean result.
func AsBool() Option {
	return func(c *conf.Config) {
		c.Expect = reflect.Bool
// AsInt64 tells the compiler to expect int64 result.
func AsInt64() Option {
	return func(c *conf.Config) {
		c.Expect = reflect.Int64
// AsFloat64 tells the compiler to expect float64 result.
func AsFloat64() Option {
	return func(c *conf.Config) {
		c.Expect = reflect.Float64
// Optimize turns optimizations on or off.
func Optimize(b bool) Option {
	return func(c *conf.Config) {
		c.Optimize = b
// Compile parses and compiles given input expression to bytecode program.
func Compile(input string, ops ...Option) (*vm.Program, error) {
	config := &conf.Config{
		Operators: make(map[string][]string),
		Optimize:  true,
	for _, op := range ops {
		op(config)
	if err := config.Check(); err != nil {
		return nil, err
	tree, err := parser.Parse(input)
	if err != nil {
		return nil, err
	if config.Types != nil {
		_, err = checker.Check(tree, config)
		if err != nil {
			return nil, err
		checker.PatchOperators(tree, config)
	if config.Optimize {
		optimizer.Optimize(&tree.Node)
	program, err := compiler.Compile(tree, config)
	if err != nil {
		return nil, err
	return program, nil
// Parse parses input string to a program.
// Deprecated: use expr.Compile instead.
func Parse(input string, ops ...Option) (*vm.Program, error) {
	return Compile(input, ops...)
// Run evaluates given bytecode program.
func Run(program *vm.Program, env interface{}) (interface{}, error) {
	return vm.Run(program, env)

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