eval

package

v0.0.0-...-0deda60 Latest Latest Go to latest Published: Mar 23, 2020 License: MIT Imports: 5 Imported by: 0

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Repository

github.com/slackbuffer/digest_gopl

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Documentation ¶

Overview ¶

Package eval is an evaluator for simple arithmetic expressions

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

Constants ¶

This section is empty.

Variables ¶

This section is empty.

Functions ¶

This section is empty.

Types ¶

type Env ¶

type Env map[Var]float64

Env is an environment that maps variable name to values

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
}

An Expr is an arithmetic expresson

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
     | id '(' expr ',' ... ')'     a function call
     | '-' expr                    a unary operator (+-)
     | expr '+' expr               a binary operator (+-*/)

type Var ¶

type Var string

A Var represents a reference to a variable

func (Var) Check ¶

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

func (Var) Eval ¶

func (v Var) Eval(env Env) float64

Eval is an environment that maps variable name to values

Source Files ¶

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