func (l *Lexer) lexInput() {
// set up to lex an input
in := <-l.inputs
l.str = in
l.length = len(in)
l.pos = 0
l.runePeeked = false
// until input is done or error
for {
select {
// abandon input
case <-l.messageOut:
l.messageBack <- "lexer: breaking"
l.tokens <- token.New(token.EOF, "EOF")
return
// continue input
default:
t := l.lexToken()
l.tokens <- t
if t.Type == token.EOF {
return
}
}
}
}
// lex next token of input
func (l *Lexer) lexToken() token.Item {
switch r := l.peekRune(); {
// skip whitespace and comments, find next token
case isSpace(r):
l.nextRune()
return l.lexToken()
case r == ';':
l.skipComment()
return l.lexToken()
// parenthesis
case r == '(':
l.nextRune()
return token.New(token.LParen, "(")
case r == ')':
l.nextRune()
return token.New(token.RParen, ")")
// constant
case r == '#':
constant := l.lexConst()
return token.New(token.Const, constant)
// quote
case r == '\'':
l.nextRune()
return token.New(token.Quote, "'")
// end of file
case r == eof:
return token.New(token.EOF, "EOF")
// otherwise symbol
default:
sym := l.lexSym()
return token.New(token.Sym, sym)
}
}