refactor input_reader class and its use in lexer * input.h, input.cc (base_reader::get_input, file_reader::get_input, terminal_reader::get_input, eval_string_reader::get_input): Accept prompt as argument. Change all uses. (base_reader::octave_gets): Accept prompt as argument instead of getting it from input_system. Change all uses. * interpreter.cc (interpreter::main_loop): Get promptflag from parser, prompt string from input_system, decode it here, and pass to the input reader. * lex.h, lex.ll (base_lexer::m_promptflag): New data member. (base_lexer::reset): Also reset m_promptflag. (base_lexer::increment_promptflag, base_lexer::decrement_promptflag, base_lexer::promptflag): No longer virtual. (lexer::increment_promptflag, lexer::decrement_promptflag, lexer::promptflag): Delete. (push_lexer::m_pflag): Delete. (push_lexer::increment_promptflag, push_lexer::decrement_promptflag, push_lexer::promptflag): Delete. (push_lexer::reset): Delete. (lexer::fill_flex_buffer): Get prompt string from input_system, decode it here, and pass to the input reader. * parse.h (base_parser::increment_promptflag, base_parser::decrement_promptflag, base_parser::promptflag): New convenience functions.

--- a/libinterp/corefcn/input.h	Fri Oct 18 07:41:02 2019 -0400
+++ b/libinterp/corefcn/input.h	Fri Oct 18 09:08:06 2019 -0400
@@ -207,7 +207,7 @@
 
     virtual ~base_reader (void) = default;
 
-    virtual std::string get_input (bool& eof) = 0;
+    virtual std::string get_input (const std::string& prompt, bool& eof) = 0;
 
     virtual std::string input_source (void) const { return s_in_src; }
 
@@ -226,7 +226,7 @@
       return retval;
     }
 
-    std::string octave_gets (bool& eof);
+    std::string octave_gets (const std::string& prompt, bool& eof);
 
     virtual bool input_from_terminal (void) const { return false; }
 
@@ -271,9 +271,9 @@
 
     int promptflag (int n) { return m_rep->promptflag (n); }
 
-    std::string get_input (bool& eof)
+    std::string get_input (const std::string& prompt, bool& eof)
     {
-      return m_rep->get_input (eof);
+      return m_rep->get_input (prompt, eof);
     }
 
     std::string input_source (void) const