From 5dddc9d9c2f39547c95542b458575f38d6aca539 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Mon, 12 Feb 2018 08:35:34 -0800
Subject: New listener variable: *listener-pprint-s*.

* parser.c (listener_pprint_s): New symbol variable.
(repl): Check new variable after each evaluation and print
accordingly.
(parse_init): Initialize listener_print_s with interned symbol
and register the variable.

* txr.1: Document *listener-pprint-s*.
---
 parser.c |  7 ++++++-
 txr.1    | 21 +++++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/parser.c b/parser.c
index 4f4bcdae..b47e642f 100644
--- a/parser.c
+++ b/parser.c
@@ -62,6 +62,7 @@
 
 val parser_s, unique_s, circref_s;
 val listener_hist_len_s, listener_multi_line_p_s, listener_sel_inclusive_p_s;
+val listener_pprint_s;
 val rec_source_loc_s;
 val intr_s;
 
@@ -1140,6 +1141,7 @@ val repl(val bindings, val in_stream, val out_stream)
   val hist_len_var = lookup_global_var(listener_hist_len_s);
   val multi_line_var = lookup_global_var(listener_multi_line_p_s);
   val sel_inclusive_var = lookup_global_var(listener_sel_inclusive_p_s);
+  val pprint_var = lookup_global_var(listener_pprint_s);
   val rw_f = func_f1v(out_stream, repl_warning);
   val saved_dyn_env = set_dyn_env(make_env(nil, nil, dyn_env));
 
@@ -1240,9 +1242,10 @@ val repl(val bindings, val in_stream, val out_stream)
                         eval_intrinsic(form, nil),
                         read_eval_ret_last(nil, prev_counter,
                                            in_stream, out_stream));
+        val pprin = cdr(pprint_var);
         reg_varl(var_sym, value);
         sethash(result_hash, var_counter, value);
-        prinl(value, out_stream);
+        if3(pprin, pprinl, prinl)(value, out_stream);
         lino_set_result(ls, utf8_dup_to(c_str(tostring(value))));
         lino_hist_add(ls, line_u8);
       }
@@ -1324,6 +1327,7 @@ void parse_init(void)
   listener_hist_len_s = intern(lit("*listener-hist-len*"), user_package);
   listener_multi_line_p_s = intern(lit("*listener-multi-line-p*"), user_package);
   listener_sel_inclusive_p_s = intern(lit("*listener-sel-inclusive-p*"), user_package);
+  listener_pprint_s = intern(lit("*listener-pprint-p*"), user_package);
   rec_source_loc_s = intern(lit("*rec-source-loc*"), user_package);
   unique_s = gensym(nil);
   prot1(&stream_parser_hash);
@@ -1333,6 +1337,7 @@ void parse_init(void)
   reg_var(listener_hist_len_s, num_fast(500));
   reg_var(listener_multi_line_p_s, t);
   reg_var(listener_sel_inclusive_p_s, nil);
+  reg_var(listener_pprint_s, nil);
   reg_var(rec_source_loc_s, nil);
   reg_fun(circref_s, func_n1(circref));
 }
diff --git a/txr.1 b/txr.1
index ef9dab94..dbde5745 100644
--- a/txr.1
+++ b/txr.1
@@ -62500,6 +62500,27 @@ that the selection is determined by the starting and ending character,
 and includes them. This type of selection pairs well with a block-shaped
 cursor.
 
+.coNP Special variable @ *listener-pprint-p*
+.desc
+This Boolean variable controls how the listener prints the results
+of evaluations.
+It is
+.code nil
+by default.
+
+When the variable is
+.codn nil ,
+the evaluation result of each line entered into the listener is printed
+using the
+.code prinl
+function. Thus values are rendered in a machine-readable syntax, ensuing
+read/print consistency.
+
+If the variable is set true, the evaluation result of each line is printed
+using the
+.code pprinl
+function.
+
 .SH* SETUID/SETGID OPERATION
 
 On platforms with the Unix filesystem and process security model, \*(TX has
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