Generic Go lexer

import "src.userspace.com.au/lexer"

// Define the tokens for the lexer.
const (
    _ lexer.TokenType = iota
    tBREStart
    tBREEnd
    tRangeStart
    tRangeDash
    tRangeEnd
    tCharacter
    tClass
    tNot
)

// Define states returning a StateFunc.
func startState(l *lexer.Lexer) lexer.StateFunc {
    l.SkipWhitespace()
    r := l.Next()
    if r != '[' {
        return l.Error("expecting [")
    }
    l.Emit(tBREStart)
    return beFirstState
}