Why the lex-mode and bison-mode are removed from emacs ?

[charles]

Hi my friends,

I'm programming in flex & bison in these days, but I'm not
comfortable by using c-mode to compose the .l and .y.c. So
I'm looking for the specified mode for lex and yacc. But I
realized that they might be present in early phase but not
the current release of emacs. Why they are removed? What
major mode or minor mode are the good replacement of them?

Thanks very much.

Charles   June 13, 2002.