(Vprint_gensym_alist): Renamed from printed_gensyms.

(Vprint_gensym): Now a Lisp_Object; Renamed from print_gensym.
(syms_of_print): Set up both as Lisp vars.
(PRINTPREPARE, PRINTFINISH): Don't clear Vprint_gensym_alist
if Vprint_gensym is a cons cell.

1 files changed, 32 insertions, 16 deletions

diff --git a/src/print.c b/src/print.c
index b399d63c091..41159ae69da 100644
--- a/src/print.c
+++ b/src/print.c
@@ -83,15 +83,17 @@ Lisp_Object Qprint_escape_newlines;
 
 int print_quoted;
 
-/* Nonzero means print #: before uninterned symbols.  */
+/* Non-nil means print #: before uninterned symbols.
+   Neither t nor nil means so that and don't clear Vprint_gensym_alist
+   on entry to and exit from print functions.  */
 
-int print_gensym;
+Lisp_Object Vprint_gensym;
 
 /* Association list of certain objects that are `eq' in the form being
    printed and which should be `eq' when read back in, using the #n=object
    and #n# reader forms.  Each element has the form (object . n).  */
 
-Lisp_Object printed_gensyms;
+Lisp_Object Vprint_gensym_alist;
 
 /* Nonzero means print newline to stdout before next minibuffer message.
    Defined in xdisp.c */
@@ -208,7 +210,8 @@ glyph_to_str_cpy (glyphs, str)
          }                                                      \
        print_buffer_pos = 0;                                    \
      }                                                          \
-   printed_gensyms = Qnil
+   if (!CONSP (Vprint_gensym))                                  \
+     Vprint_gensym_alist = Qnil
 
 #define PRINTFINISH                                     \
    if (NILP (printcharfun))                             \
@@ -226,7 +229,8 @@ glyph_to_str_cpy (glyphs, str)
                           ? PT - start_point : 0));     \
    if (old != current_buffer)                           \
      set_buffer_internal (old);                         \
-   printed_gensyms = Qnil
+   if (!CONSP (Vprint_gensym))                          \
+     Vprint_gensym_alist = Qnil
 
 #define PRINTCHAR(ch) printchar (ch, printcharfun)
 
@@ -1047,12 +1051,12 @@ print (obj, printcharfun, escapeflag)
         /* If we print an uninterned symbol as part of a complex object and
            the flag print-gensym is non-nil, prefix it with #n= to read the
            object back with the #n# reader syntax later if needed.  */
-        if (print_gensym && NILP (XSYMBOL (obj)->obarray))
+        if (! NILP (Vprint_gensym) && NILP (XSYMBOL (obj)->obarray))
           {
             if (print_depth > 1)
               {
                 Lisp_Object tem;
-                tem = Fassq (obj, printed_gensyms);
+                tem = Fassq (obj, Vprint_gensym_alist);
                 if (CONSP (tem))
                   {
                     PRINTCHAR ('#');
@@ -1062,11 +1066,11 @@ print (obj, printcharfun, escapeflag)
                   }
                 else
                   {
-                    if (CONSP (printed_gensyms))
-                      XSETFASTINT (tem, XFASTINT (XCDR (XCAR (printed_gensyms))) + 1);
+                    if (CONSP (Vprint_gensym_alist))
+                      XSETFASTINT (tem, XFASTINT (XCDR (XCAR (Vprint_gensym_alist))) + 1);
                     else
                       XSETFASTINT (tem, 1);
-                    printed_gensyms = Fcons (Fcons (obj, tem), printed_gensyms);
+                    Vprint_gensym_alist = Fcons (Fcons (obj, tem), Vprint_gensym_alist);
 
                     PRINTCHAR ('#');
                     print (tem, printcharfun, escapeflag);
@@ -1505,10 +1509,25 @@ I.e., (quote foo) prints as 'foo, (function foo) as #'foo, and, backquoted\n\
 forms print in the new syntax.");
   print_quoted = 0;
 
-  DEFVAR_BOOL ("print-gensym", &print_gensym,
+  DEFVAR_LISP ("print-gensym", &Vprint_gensym,
     "Non-nil means print uninterned symbols so they will read as uninterned.\n\
-I.e., the value of (make-symbol "foobar") prints as #:foobar.");
-  print_gensym = 0;
+I.e., the value of (make-symbol "foobar") prints as #:foobar.\n\
+When the uninterned symbol appears within a larger data structure,\n\
+in addition use the #...# and #...= constructs as needed,\n\
+so that multiple references to the same symbol are shared once again\n\
+when the text is read back.\n\
+\n\
+If the value of `print-gensym' is a cons cell, then in addition refrain from\n\
+clearing `print-gensym-alist' on entry to and exit from printing functions,\n\
+so that the use of #...# and #...= can carry over for several separately\n\
+printed objects.");
+  Vprint_gensym = Qnil;
+
+  DEFVAR_LISP ("print-gensym-alist", &Vprint_gensym_alist,
+    "Association list of elements (GENSYM . N) to guide use of #N# and #N=.\n\
+In each element, GENSYM is an uninterned symbol that has been associated\n\
+with #N= for the specified value of N.");
+  Vprint_gensym_alist = Qnil;
 
   /* prin1_to_string_buffer initialized in init_buffer_once in buffer.c */
   staticpro (&Vprin1_to_string_buffer);
@@ -1528,9 +1547,6 @@ I.e., the value of (make-symbol "foobar") prints as #:foobar.");
   Qprint_escape_newlines = intern ("print-escape-newlines");
   staticpro (&Qprint_escape_newlines);
 
-  staticpro (&printed_gensyms);
-  printed_gensyms = Qnil;
-
 #ifndef standalone
   defsubr (&Swith_output_to_temp_buffer);
 #endif /* not standalone */