-AC_CHECK_FILE([ginsh/ginsh_parser.h], [],
- [AS_IF([test -z "$YACCEXE"], [GINAC_WARNING([ginsh will not compile, because yacc/bison is missing.])])])
-AC_CHECK_FILE([ginsh/ginsh_lexer.cc], [],
- [AS_IF([test x"$LEX" == x":"], [GINAC_WARNING([ginsh will not compile, because lex/flex is missing.])])])
+dnl Python is necessary for building function.{cpp,h}
+AC_PATH_PROG(PYTHON, python, "")
+AS_IF([test -z "$PYTHON" -a ! -f "$srcdir/ginac/function.cpp"],
+ [AC_MSG_ERROR([GiNaC will not compile because Python is missing])])