calc

Documentation

Index

• Constants
• func Calc(input string) (float64, error)
• func CalcAndCompare(input string) (float64, error)
• func Eval(exp Expression) float64
• type Expression
• type InfixExpression
  • func (ie *InfixExpression) String() string
• type IntegerLiteralExpression
  • func (il *IntegerLiteralExpression) String() string
• type Lexer
  • func NewLex(input string) *Lexer
  • func (l *Lexer) NextToken() Token
• type Parser
  • func NewParser(l *Lexer) *Parser
  • func (p *Parser) Errors() []string
  • func (p *Parser) ParseExpression(precedence int) Expression
• type PrefixExpression
  • func (pe *PrefixExpression) String() string
• type Token

Constants

const (
	ILLEGAL = "ILLEGAL"
	EOF     = "EOF"
	FLOAT   = "FLOAT"

	PLUS     = "+"
	MINUS    = "-"
	ASTERISK = "*"
	SLASH    = "/"

	LPAREN = "("
	RPAREN = ")"
)

const (
	LOWEST  int
	SUM     // +, -
	PRODUCT // *, /
	PREFIX  // -X
	CALL    // (X)
)

Functions

func Calc

func Calc(input string) (float64, error)

四则运算

func CalcAndCompare

func CalcAndCompare(input string) (float64, error)

四则运算和比较运算

func Eval

func Eval(exp Expression) float64

Types

type Expression

type Expression interface {
	String() string
}

type InfixExpression

type InfixExpression struct {
	Token    Token
	Left     Expression
	Operator string
	Right    Expression
}

func (*InfixExpression) String

func (ie *InfixExpression) String() string

type IntegerLiteralExpression

type IntegerLiteralExpression struct {
	Token Token
	Value float64
}

func (*IntegerLiteralExpression) String

func (il *IntegerLiteralExpression) String() string

type Lexer

type Lexer struct {
	// contains filtered or unexported fields
}

词法分析器

func NewLex

func NewLex(input string) *Lexer

func (*Lexer) NextToken

func (l *Lexer) NextToken() Token

词法分析器的核心函数,用于获取下一个词元。针对不同字符返回不同的Token结构值

type Parser

type Parser struct {
	// contains filtered or unexported fields
}

func NewParser

func NewParser(l *Lexer) *Parser

func (*Parser) Errors

func (p *Parser) Errors() []string

func (*Parser) ParseExpression

func (p *Parser) ParseExpression(precedence int) Expression

type PrefixExpression

type PrefixExpression struct {
	Token    Token
	Operator string
	Right    Expression
}

func (*PrefixExpression) String

func (pe *PrefixExpression) String() string

type Token

type Token struct {
	Type    string //对应我们上面的词元类型
	Literal string // 实际的string字符
}

词元