ch7_eval

package
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Published: May 18, 2020 License: Apache-2.0 Imports: 5 Imported by: 0

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Constants

This section is empty.

Variables

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Functions

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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
}

An Expr is an arithmetic expression.

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 identifies a variable, e.g., x

func (Var) Check

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

func (Var) Eval

func (v Var) Eval(env Env) float64

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