expr

Documentation

Index

• 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 (v Var) String() string

Types

type Env

type Env map[Var]float64

type Expr

type Expr interface {
	Eval(env Env) float64
	// Check reports errors in this Expr and adds its Vars to the set.
	Check(vars map[Var]bool) error
	fmt.Stringer
}

func Parse

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

Parse parses the input string as an arithmetic expression.

  expr = num                         a literal number, e.g., 3.14159
       | id                          a variable name, e.g., x
	  | 'min' '(' expr ',' expr ')' the min operator, e.g., min(1, 2) => 1
       | id '(' expr ',' ... ')'     a function call
       | '-' expr                    a unary operator (+-)
       | expr '+' expr               a binary operator (+-*/)

type Var

type Var string

func (Var) Check

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

func (Var) Eval

func (v Var) Eval(env Env) float64

func (Var) String

func (v Var) String() string