evaluator

README

evaluator

A simple library for expression evaluation.

SYNOPSIS

    e, err := evaluator.New("(var1 + 0.5) * var2")
    if err != nil {
        log.Fatal(err)
    }
	ans, err := e.Eval(evaluator.Variables{"var1": 0.5, "var2": 3})
    if err != nil {
        log.Fatal(err)
    }
	fmt.Println(ans)

see godoc.org/github.com/mashiike/evaluator.

Author

Copyright (c) 2021 Mashiike.

LICENSE

MIT

Documentation

Index

• Variables
• func IsDivideByZero(err error) bool
• func IsVariableNotFound(err error) bool
• type Comparator
• type Evaluator
  • func New(expr string) (Evaluator, error)
• type NumOfArgumentsMismatchError
  • func (e *NumOfArgumentsMismatchError) Error() string
• type Variables

Variables

var (
	ErrDivideByZero     = errors.New("divide by 0")
	ErrVariableNotFound = errors.New("variable not found")
)

reserved error

Functions

func IsDivideByZero

func IsDivideByZero(err error) bool

IsDivideByZero check error DivideByZero

func IsVariableNotFound

func IsVariableNotFound(err error) bool

IsVariableNotFound check error VariableNotFound

Types

type Comparator

type Comparator interface {
	// Compare performs an comparison by giving a set of variables.
	Compare(Variables) (bool, error)

	fmt.Stringer
}

Comparator is a special Evaluator whose evaluation expression is a comparison expression.

type Evaluator

type Evaluator interface {
	// Eval performs an evaluation by giving a set of variables.
	Eval(Variables) (interface{}, error)

	//Strict sets the expression evaluation to run in strict mode. The default is false.
	//For example, the behavior changes when the variable is not set.
	//  Referenced as nil if Strict is set to false.
	//  If set to true, the expression evaluation will be Error.
	Strict(bool)

	// AsComparator attempts to convert to Comparator
	AsComparator() (Comparator, bool)

	fmt.Stringer
}

Evaluator is a variable evaluator created based on one expression

func New

func New(expr string) (Evaluator, error)

New parses the expression to create an evaluator

type NumOfArgumentsMismatchError

type NumOfArgumentsMismatchError struct {
	FunctionName string
	Expected     int
	Given        int
}

NumOfArgumentsMismatchError is an error that occurs when the number of arguments of the called function is different.

func (*NumOfArgumentsMismatchError) Error

func (e *NumOfArgumentsMismatchError) Error() string

type Variables

type Variables map[string]interface{}

Variables are a group of variables given to the evaluator