waiig15/token/token.go

package token

// TokenType is the string representation of the Token types.
type TokenType string

// Token represents a Parser token.
type Token struct {
	Type    TokenType
	Literal string
}

// The TokenType values.
const (
	ILLEGAL = "ILLEGAL"
	EOF     = "EOF"

	// Identifiers + literals.
	IDENT = "IDENT" // add, foobar, x, y, ...
	INT   = "INT"   // 123456, ...

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

	LT     = "<"
	GT     = ">"
	EQ     = "=="
	NOT_EQ = "!="

	// Delimiters.
	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,
}

// LookupIdent checks the keywords table to see whether the given identifier is
// in fact a keyword.
func LookupIdent(ident string) TokenType {
	if tok, ok := keywords[ident]; ok {
		return tok
	}
	return IDENT
}