lexer

Documentation

Overview

Package lexer converts source code into tokens. Tokens are indivisible units that are used by the parser package to create the AST structures that represent the source code.

Index

• Constants
• type Options
• type Token
  • func NewToken(kind, value string) Token
  • func TokenizeString(str string, options Options) ([]Token, []*ast.Comment, error)
  • func (t Token) String() string

Constants

const (
	TokenEOF = "end of file"

	// Dynamic
	TokenBoolLiteral   = "bool literal"   // boolean literal, eg. true
	TokenCharLiteral   = "char literal"   // char literal, eg. 'a'
	TokenComment       = "comment"        // eg. "//..."
	TokenDataLiteral   = "data literal"   // data literal, eg. `foo`
	TokenIdentifier    = "identifier"     // any non-keyword
	TokenNumberLiteral = "number literal" // number literal, eg. 12.3
	TokenStringLiteral = "string literal" // string literal, eg. "hello"

	// Keywords
	TokenAnd      = "and"
	TokenAny      = "any"
	TokenAssert   = "assert"
	TokenBool     = "bool"
	TokenBreak    = "break"
	TokenCase     = "case"
	TokenChar     = "char"
	TokenContinue = "continue"
	TokenData     = "data"
	TokenElse     = "else"
	TokenFor      = "for"
	TokenFunc     = "func"
	TokenIf       = "if"
	TokenImport   = "import"
	TokenIn       = "in"
	TokenNot      = "not"
	TokenNumber   = "number"
	TokenOr       = "or"
	TokenReturn   = "return"
	TokenString   = "string"
	TokenSwitch   = "switch"
	TokenTest     = "test"

	// Operators
	TokenAssign           = "="
	TokenColon            = ":"
	TokenComma            = ","
	TokenCurlyClose       = "}"
	TokenCurlyOpen        = "{"
	TokenDecrement        = "--"
	TokenDivide           = "/"
	TokenDivideAssign     = "/="
	TokenDot              = "."
	TokenEqual            = "=="
	TokenGreaterThan      = ">"
	TokenGreaterThanEqual = ">="
	TokenIncrement        = "++"
	TokenLessThan         = "<"
	TokenLessThanEqual    = "<="
	TokenMinus            = "-"
	TokenMinusAssign      = "-="
	TokenNotEqual         = "!="
	TokenParenClose       = ")"
	TokenParenOpen        = "("
	TokenPlus             = "+"
	TokenPlusAssign       = "+="
	TokenRemainder        = "%"
	TokenRemainderAssign  = "%="
	TokenSemiColon        = ";"
	TokenSquareClose      = "]"
	TokenSquareOpen       = "["
	TokenTimes            = "*"
	TokenTimesAssign      = "*="
)

Tokens defined here have a human-readable name used in error messages. You should not rely on these values staying the same, only that their value will be unique amongst the defined tokens.

Types

type Options

type Options struct {
	// IncludeComments will include TokenComment in the returned tokens.
	IncludeComments bool
}

Options allows configuration of the lexer.

type Token

type Token struct {
	// Kind will be one of the Token* constants.
	Kind string

	// Value is captured from the original source code. It is only useful for
	// dynamic tokens such as TokenString or TokenIdentifier.
	Value string

	// IsEndOfLine will be true if there is at least one new line character
	// after this token (ignoring other whitespace). This is needed by some
	// grammars to determine the end of the line, but newlines have no effect in
	// between most tokens.
	//
	// One exception to this is comments. Comment always have to be terminated
	// by a new line, however, IsEndOfLine will only be true if the comment is
	// followed by an empty line. This is because IsEndOfLine is also used by
	// the lexer to determine if comments are part of the same block as their
	// previous lines and/or if they might be attached to functions are
	// documentation.
	IsEndOfLine bool
}

Token represents a single token.

func NewToken

func NewToken(kind, value string) Token

NewToken initializes a token with a kind and value and other defaults.

func TokenizeString

func TokenizeString(str string, options Options) ([]Token, []*ast.Comment, error)

TokenizeString returns a slice of tokens from the provided str.

func (Token) String

func (t Token) String() string

String returns a human-readable representation of the token.