parser.h: Document copline with more detail

It took me a while to figure this out, so here it is for
future readers.

diff --git a/parser.h b/parser.h
index 0e5a8e3..16b756f 100644 (file)
--- a/parser.h
+++ b/parser.h
@@ -81,7 +81,11 @@ typedef struct yy_parser {
     char       *linestart;     /* beginning of most recently read line */
     char       *last_uni;      /* position of last named-unary op */
     char       *last_lop;      /* position of last list operator */
-    line_t     copline;        /* current line number */
+    /* copline is used to pass a specific line number to newSTATEOP.  It
+       is a one-time line number, as newSTATEOP invalidates it (sets it to
+       NOLINE) after using it.  The purpose of this is to report line num-
+       bers in multiline constructs using the number of the first line. */
+    line_t     copline;
     U16                in_my;          /* we're compiling a "my"/"our" declaration */
     U8         lex_state;      /* next token is determined */
     U8         error_count;    /* how many compile errors so far, max 10 */