eval

Documentation

Overview

Package eval provides an expression evaluator.

Index

• func Format(e Expr) string
• type Env
• type Expr
  • func Parse(input string) (_ Expr, err error)
• type Var
  • func (v Var) Check(vars map[Var]bool) error
  • func (v Var) Eval(env Env) float64
  • func (e Var) String() string

Functions

func Format

func Format(e Expr) string

Format formats an expression as a string.

Types

type Env

type Env map[Var]float64

Env represents environment for executing expression.

type Expr

type Expr interface {
	// Eval returns the value of this Expr in the environment env.
	Eval(env Env) float64
	// Check reports errors in this Expr and adds its Vars to the set.
	Check(vars map[Var]bool) error
	// String returns string representation of expression.
	String() string
}

An Expr is an arithmetic expression.

func Parse

func Parse(input string) (_ Expr, err error)

Parse parses the input string as an arithmetic expression.

type Var

type Var string

A Var identifies a variable, e.g., x.

func (Var) Check

func (v Var) Check(vars map[Var]bool) error

Check verifies that variable meets requriments.

func (Var) Eval

func (v Var) Eval(env Env) float64

Eval transforms string representation of var to value.

func (Var) String

func (e Var) String() string