- * Main parse routine for an opened file. This is called for each
- * opened file and simply loops around the full input file, possibly
- * nesting (i.e., with `so').
+ * Main parse routine for a buffer.
+ * It assumes encoding and line numbering are already set up.
+ * It can recurse directly (for invocations of user-defined
+ * macros, inline equations, and input line traps)
+ * and indirectly (for .so file inclusion).