calc

README

calc

Calc is a package that provides the tools to evaluate simple numerical expressions.

Fork from github.com/marcak/calc, a bit refactored, with errors, with tests and as go module.

Documentation

Index

• func ContainsLetter(s string) bool
• func IsOperator(r rune) bool
• func Solve(s string) (float64, error)
• func SolveFunction(s string) (string, error)
• func SolvePostfix(tokens Stack) (float64, error)
• type Parser
  • func NewParser(r io.Reader) *Parser
  • func (p *Parser) Parse() (Stack, error)
  • func (p *Parser) Scan() (Token, error)
  • func (p *Parser) ScanIgnoreWhitespace() (Token, error)
  • func (p *Parser) Unscan()
• type Scanner
  • func NewScanner(r io.Reader) *Scanner
  • func (s *Scanner) Read() (rune, error)
  • func (s *Scanner) Scan() (Token, error)
  • func (s *Scanner) ScanNumber() (Token, error)
  • func (s *Scanner) ScanWhitespace() (Token, error)
  • func (s *Scanner) ScanWord() (Token, error)
  • func (s *Scanner) Unread() error
• type Stack
  • func ShuntingYard(s Stack) (Stack, error)
  • func (s *Stack) EmptyInto(dest *Stack)
  • func (s *Stack) IsEmpty() bool
  • func (s *Stack) Length() int
  • func (s *Stack) Peek() Token
  • func (s *Stack) Pop() Token
  • func (s *Stack) Push(i ...Token)
• type Token
• type TokenType

Functions

func ContainsLetter

func ContainsLetter(s string) bool

ContainsLetter checks if a string contains a letter

func IsOperator

func IsOperator(r rune) bool

func Solve

func Solve(s string) (float64, error)

Solve a mathematical calculation.

func SolveFunction

func SolveFunction(s string) (string, error)

SolveFunction returns the answer of a function found within an expression

func SolvePostfix

func SolvePostfix(tokens Stack) (float64, error)

SolvePostfix evaluates and returns the answer of the expression converted to postfix

Types

type Parser

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

func NewParser

func NewParser(r io.Reader) *Parser

func (*Parser) Parse

func (p *Parser) Parse() (Stack, error)

func (*Parser) Scan

func (p *Parser) Scan() (Token, error)

func (*Parser) ScanIgnoreWhitespace

func (p *Parser) ScanIgnoreWhitespace() (Token, error)

func (*Parser) Unscan

func (p *Parser) Unscan()

type Scanner

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

func NewScanner

func NewScanner(r io.Reader) *Scanner

func (*Scanner) Read

func (s *Scanner) Read() (rune, error)

func (*Scanner) Scan

func (s *Scanner) Scan() (Token, error)

func (*Scanner) ScanNumber

func (s *Scanner) ScanNumber() (Token, error)

func (*Scanner) ScanWhitespace

func (s *Scanner) ScanWhitespace() (Token, error)

func (*Scanner) ScanWord

func (s *Scanner) ScanWord() (Token, error)

func (*Scanner) Unread

func (s *Scanner) Unread() error

type Stack

type Stack []Token

Stack is a LIFO data structure.

func ShuntingYard

func ShuntingYard(s Stack) (Stack, error)

func (*Stack) EmptyInto

func (s *Stack) EmptyInto(dest *Stack)

EmptyInto dumps all tokens from one stack to another.

func (*Stack) IsEmpty

func (s *Stack) IsEmpty() bool

IsEmpty checks if there are any tokens in the stack.

func (*Stack) Length

func (s *Stack) Length() int

Length returns the amount of tokens in the stack.

func (*Stack) Peek

func (s *Stack) Peek() Token

Peek returns the token at the top of the stack.

func (*Stack) Pop

func (s *Stack) Pop() Token

Pop removes the token at the top of the stack and returns its value.

func (*Stack) Push

func (s *Stack) Push(i ...Token)

Push adds tokens to the top of the stack.

type Token

type Token struct {
	// Type of the token.
	// This can be used to parse the Value accordingly.
	Type TokenType

	// Value of the Token.
	// It should match the Type.
	Value string
}

Token represents a pair of a type and a value which matches that type.

type TokenType

type TokenType int

TokenType defines what the token is.

const (
	Number TokenType = iota
	Lparen
	Rparen
	Constant
	Function
	Operator
	Whitespace
)

These constants are all possible TokenType values.