package token type TokenType string const ( ILLEGAL = "ILLEGAL" EOF = "EOF" // Identifiers + literals IDENT = "IDENT" // add, foobar, x, y, ... INT = "INT" // 1343456 // 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" ) type Token struct { Type TokenType Literal string } 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 }