eval

package

v0.0.0-...-4489971 Latest Latest Go to latest Published: Apr 5, 2024 License: MIT Imports: 6 Imported by: 0

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Repository

github.com/bewuethr/gopl

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Documentation ¶

Overview ¶

Package eval provides an expression evaluator.

Index ¶

type Env
type Expr
- func Parse(input string) (_ Expr, err error)
type Var

Constants ¶

This section is empty.

Variables ¶

This section is empty.

Functions ¶

This section is empty.

Types ¶

type Env ¶

type Env map[Var]float64

An Env is an environment of float variables.

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
	// Print pretty-prints an expression.
	Print() 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.

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

Eval evaluates the variable v, i.e., looks it up in the environment.

func (Var) Print ¶

func (v Var) Print() string

Print prints variable v.

Source Files ¶

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