ll1/common/common.go

// Common interfaces and shared functions for the ll1 module.
package common

import "regexp"
import "strings"
import "fmt"

type Location struct {
	Name *string
	Line int
	Col  int
}

func (p Location) String() string {
	name := "<input>"
	if p.Name != nil {
		name = *p.Name
	}
	return fmt.Sprintf("%s:%d:%d:", name, p.Line, p.Col)
}

// Kind is the kind of token.
type Kind int

const (
	SkipKind  Kind = -30000
	ErrorKind Kind = -31000
)

type Action func(f Lexer, k Kind, matches ...string) []Token

// Value is the value of a token, can be string value, integer
// or some other custom value
type Value interface {
	Value() Value
	String() string
}

type StringValue string

func (sv StringValue) Value() Value {
	return sv
}

func (sv StringValue) String() string {
	return string(sv)
}

type ErrorValue struct {
	Err error
}

func (ev ErrorValue) Value() Value {
	return ev
}

func (ev ErrorValue) String() string {
	return string(ev.Err.Error())
}

type IntValue int64

func (iv IntValue) Value() Value {
	return iv
}

func (iv IntValue) String() string {
	return fmt.Sprintf("%d", iv)
}

type FloatValue int64

func (fv FloatValue) Value() Value {
	return fv
}

func (fv FloatValue) String() string {
	return fmt.Sprintf("%d", fv)
}

type Token interface {
	Location() Location
	Kind() Kind
	Text() string
	Value() Value
}

type Lexer interface {
	// Accept will accept a regexp and advance, returning the matches.
	// Returns nil if no matches were found.
	Accept(re *regexp.Regexp) []string
	// Returns the current lexer Location.
	Location() Location
	// Returns if the lexer is at the end or not.
	EOF() bool

	// The lexer creates a token with the current lexer Location and
	// the given kind and text.
	MakeToken(kind Kind, form string, args ...interface{}) Token

	// The lexer creates a token with the current lexer Location and
	// the given kind. The text is taken from the lexer string builder and
	// that builser is reset.
	MakeBuilderToken(kind Kind) Token

	// The lexer has a string builder, which can be used to append
	// strings or runes to and which can be returned and cleared when the
	// token is complete.
	Builder() *strings.Builder

	// Lexeme adds a lexeme to the lexer.
	Lexeme(kind Kind, re, context string, act Action) error
	// Calls the lexer once.
	LexOnce() []Token

	// Returns the current lexer context
	Context() string
	// Pushes the named context on the lexer context stack
	PushContext(name string)
	// Pops the current context from the lexer context stack.
	PopContext()
}