^/$ in lexical analyzers

I can see how ^ and $ regexps would be implemented using a stream-based
lexical analyzer. One just uses lookaheads and left contexts based on the
newline. What about a standard regexp package, though - i.e. one where
the object being scan- ned is simply a line? Situations like ^a|b would
seem a bit ugly, since there are no left contexts. Does one prepend a
character to the input stream, and modify the pattern (e.g. \na|\n.*b)?
Or does one use some ad hoc method?


Perhaps this question has an obvious answer. I've browsed through
standard works like the "Dragon Book," and found no- thing that is much
help (only the usual +,*,?, etc. get cov- ered).
--
      -Richard L. Goerwitz goer%midway@uchicago.bitnet
      goer@midway.uchicago.edu rutgers!oddjob!ellis!goer
--

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