A @emph{token} is the smallest meaningful element of a source program. Tokens can be strings, symbols, or instances of the @racket[token] data structure. (Plus a few other special cases, which we'll discuss later.) Usually, a token holds a single character from the source program. But sometimes it makes sense to package a sequence of characters into a single token, if the sequence has an indivisible meaning.
If possible, we also want to attach source location information to each token. Why? Because this informatino will be incorporated into the syntax objects produced by @racket[parse].
If possible, we also want to attach source location information to each token. Why? Because this information will be incorporated into the syntax objects produced by @racket[parse].
A parser often works in conjunction with a helper function called a @emph{lexer} that converts the raw code of the source program into tokens. The @racketmodname[br-parser-tools/lex] library can help us write a position-sensitive