# HG changeset patch
# User John W. Eaton <jwe@octave.org>
# Date 1570813630 14400
# Node ID cc023f049dbf718739b74d333d3e911f7a4a394a
# Parent  28ed77ca1e4a741cb5a74bea47b2fe94cae4c03a
use Bison's push parser interface in the command line REPL

Using the push parser interface moves reading input and lexical
analysis outside of the parser.  This change shows how we might
also use this arrangement to allow the GUI terminal widget to be fully
in control of gathering user input.

A new configure option allows this change to be reverted so that
Octave will use the pull parser interface that has been used in all
previous versions of Octave.

* pt-eval.cc (tree_evaluator::repl): Use conditional compilation to
choose either push or pull parser.

* configure.ac (--disable-commnad-line-push-parser): New option.
Report option setting in summary message.

diff -r 28ed77ca1e4a -r cc023f049dbf configure.ac
--- a/configure.ac	Wed Oct 16 10:16:17 2019 -0400
+++ b/configure.ac	Fri Oct 11 13:07:10 2019 -0400
@@ -1326,6 +1326,18 @@
 ## Find a termlib to use.
 OCTAVE_CHECK_LIB_TERMLIB
 
+### Use push parser by default now.
+
+ENABLE_COMMAND_LINE_PUSH_PARSER=yes
+AC_ARG_ENABLE([command-line-push-parser],
+  [AS_HELP_STRING([--disable-command-line-push-parser],
+    [don't use Bison's push parser interface in the command line REPL])],
+  [if test "$enableval" = no; then ENABLE_COMMAND_LINE_PUSH_PARSER=no; fi], [])
+if test $ENABLE_COMMAND_LINE_PUSH_PARSER = yes; then
+  AC_DEFINE(OCTAVE_ENABLE_COMMAND_LINE_PUSH_PARSER, 1,
+    [Define to 1 to use Bison's push parser interface in the command line REPL.])
+fi
+
 ### Check for ZLIB library.
 
 OCTAVE_CHECK_LIB(z, ZLIB,
@@ -3113,6 +3125,7 @@
   Build shared libraries:               $SHARED_LIBS
   Dynamic Linking API:                  $DL_API_MSG
   Include support for GNU readline:     $USE_READLINE
+  Use push parser in comand line REPL:  $ENABLE_COMMAND_LINE_PUSH_PARSER
   64-bit array dims and indexing:       $ENABLE_64
   64-bit BLAS array dims and indexing:  $HAVE_64_BIT_BLAS
   OpenMP SMP multithreading:            $ENABLE_OPENMP
diff -r 28ed77ca1e4a -r cc023f049dbf libinterp/parse-tree/pt-eval.cc
--- a/libinterp/parse-tree/pt-eval.cc	Wed Oct 16 10:16:17 2019 -0400
+++ b/libinterp/parse-tree/pt-eval.cc	Fri Oct 11 13:07:10 2019 -0400
@@ -363,13 +363,27 @@
   {
     int retval = 0;
 
-    // The parser takes ownership of the lexer and will delete it when
-    // the parser goes out of scope.
+#if defined (OCTAVE_ENABLE_COMMAND_LINE_PUSH_PARSER)
+
+    input_reader reader (m_interpreter);
+
+    // Attach input_reader object to parser so that the promptflag can
+    // be adjusted automatically when we are parsing multi-line
+    // commands.
+
+    push_parser repl_parser (m_interpreter, &reader);
+
+#else
+
+    // The pull parser takes ownership of the lexer and will delete it
+    // when the parser goes out of scope.
 
     parser repl_parser (interactive
                         ? new lexer (m_interpreter)
                         : new lexer (stdin, m_interpreter));
 
+#endif
+
     error_system& es = m_interpreter.get_error_system ();
 
     do
@@ -386,8 +400,30 @@
                 reset_debug_state ();
               }
 
+#if defined (OCTAVE_ENABLE_COMMAND_LINE_PUSH_PARSER)
+
+            do
+              {
+                bool eof;
+
+                std::string input_line = reader.get_input (eof);
+
+                if (eof)
+                  {
+                    retval = EOF;
+                    break;
+                  }
+
+                retval = repl_parser.run (input_line, false);
+              }
+            while (retval < 0);
+
+#else
+
             retval = repl_parser.run ();
 
+#endif
+
             if (retval == 0)
               {
                 std::shared_ptr<tree_statement_list> stmt_list