monkey/token/token.go

package token

type TokenType string

type Token struct {
	Type    TokenType
	Literal string
}

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

	//Identifiers and literals
	IDENT = "IDENT" //add, foo, bar, a, b, c...
	INT   = "INT"   /// 1 2 3 4 5

	//OPERATORS
	ASSIGN   = "="
	PLUS     = "+"
	MINUS    = "-"
	BANG     = "!"
	ASTERISK = "*"
	SLASH    = "/"

	LT = "<"
	GT = ">"

	//DELIM
	COMMA     = ""
	SEMICOLON = ";"

	LPAREN = "("
	RPAREN = ")"
	LBRACE = "{"
	RBRACE = "}"

	// KEYWORDS
	FUNCTION = "FUNCTION"
	LET      = "LET"
	TRUE     = "TRUE"
	FALSE    = "FALSE"
	IF       = "IF"
	ELSE     = "ELSE"
	RETURN   = "RETURN"
)

var keywords = map[string]TokenType{
	"fn":     FUNCTION,
	"let":    LET,
	"true":   TRUE,
	"false":  FALSE,
	"if":     IF,
	"else":   ELSE,
	"return": RETURN,
}

func LookupIdent(ident string) TokenType {
	if tok, ok := keywords[ident]; ok {
		return tok
	}
	return IDENT
}