token.go

package main

import (
	"fmt"
)

// TokenType is used for representing different tokens
type TokenType int

const (
	tEOF     TokenType = iota // end of file
	tError                    // error has occurred
	tComment                  // comment
	tInt                      // integer
	tFloat                    // floating point
	tIdent                    // identifier
	tString                   // string
	tNewline                  // new line
	tIllegal

	keywordBeginning
	LINE
	SCALE
	MOVE
	ROTATE
	XAXIS
	YAXIS
	ZAXIS
	SAVE
	DISPLAY
	CIRCLE
	HERMITE
	BEZIER
	BOX
	CLEAR
	SPHERE
	TORUS
	PUSH
	POP
	VARY
	BASENAME
	FRAMES
	SET
	SETKNOBS
	MESH
	LIGHT
	AMBIENT
	CONSTANTS
	keywordEnd
)

var tokens = map[TokenType]string{
	tEOF:     "EOF",
	tError:   "ERROR",
	tComment: "COMMENT",
	tInt:     "INT",
	tFloat:   "FLOAT",
	tIdent:   "IDENTIFIER",
	tString:  "STRING",
	tIllegal: "ILLEGAL",
	tNewline: "NEWLINE",

	LINE:      "line",
	SCALE:     "scale",
	MOVE:      "move",
	ROTATE:    "rotate",
	XAXIS:     "x",
	YAXIS:     "y",
	ZAXIS:     "z",
	SAVE:      "save",
	DISPLAY:   "display",
	CIRCLE:    "circle",
	HERMITE:   "hermite",
	BEZIER:    "bezier",
	BOX:       "box",
	CLEAR:     "clear",
	SPHERE:    "sphere",
	TORUS:     "torus",
	PUSH:      "push",
	POP:       "pop",
	VARY:      "vary",
	BASENAME:  "basename",
	FRAMES:    "frames",
	SET:       "set",
	SETKNOBS:  "setknobs",
	MESH:      "mesh",
	LIGHT:     "light",
	AMBIENT:   "ambient",
	CONSTANTS: "constants",
}

var keywords map[string]TokenType

func init() {
	keywords = make(map[string]TokenType)
	for i := keywordBeginning; i < keywordEnd; i++ {
		keywords[tokens[i]] = i
	}
}

// Token is a lexical token
type Token struct {
	tt    TokenType // type of token
	value string    // value of token
}

func (tt TokenType) String() string {
	if s, isToken := tokens[tt]; isToken {
		return s
	}
	return fmt.Sprint("token(", int(tt), ")")
}

func (t Token) String() string {
	return fmt.Sprintf("{%s %s}", t.tt, t.value)
}

// LookupIdent returns the corresponding token type for an identifier
func LookupIdent(ident string) TokenType {
	if tok, isKeyword := keywords[ident]; isKeyword {
		return tok
	}
	return tIllegal
}