lib/metalua/metaloop.mlua

-------------------------------------------------------------------------------
-- Copyright (c) 2006-2013 Fabien Fleutot and others.
--
-- All rights reserved.
--
-- This program and the accompanying materials are made available
-- under the terms of the Eclipse Public License v1.0 which
-- accompanies this distribution, and is available at
-- http://www.eclipse.org/legal/epl-v10.html
--
-- This program and the accompanying materials are also made available
-- under the terms of the MIT public license which accompanies this
-- distribution, and is available at http://www.lua.org/license.html
--
-- Contributors:
--     Fabien Fleutot - API and implementation
--
-------------------------------------------------------------------------------

require 'metalua.compiler'

module ('metaloop', package.seeall)

PRINT_AST  = true
LINE_WIDTH = 60
PROMPT     = "M> "
PROMPT2    = ">> "

do -- set readline() to a line reader, either editline otr a default
   local status, _ = pcall(require, 'editline')
   if status then
      local rl_handle = editline.init 'metalua'
      readline = |p| rl_handle:read(p) 
   else
      function readline (p)
         io.write (p)
         io.flush ()
         return io.read '*l'
      end
   end
end

function reached_eof(lx, msg)
   return lx:peek().tag=='Eof' or msg:find "token `Eof"
end

printf ("Metalua, interactive REPLoop.\n"..
        "(c) 2006-2011 <metalua@gmail.com>")

function run()
   local lines = { }
   while true do
      local src, lx, ast, f, results, success
      repeat
         local line = readline(next(lines) and PROMPT2 or PROMPT)
         if not line then print(); os.exit(0) end -- line==nil iff eof on stdin
         if not next(lines) then
            line = line:gsub('^%s*=', 'return ')
         end
         table.insert(lines, line)
         src = table.concat (lines, "\n")
      until #line>0
      
      lx  = mlc.luastring_to_lexstream(src) 
      success, ast = pcall(mlc.lexstream_to_ast, lx)
      if success then
         local check_status, check_msg = pcall(mlc.check_ast, ast)
         if not check_status then
             print "Invalid AST:"
             print (check_msg)
             lines = { }
         else
             success, f = pcall(mlc.ast_to_function, ast, '=stdin')
             if success then
                 results = { xpcall(f, debug.traceback) }
                 success = table.remove (results, 1)
                 if success then
                     -- Success!
                     table.iforeach(|x| table.print(x, LINE_WIDTH), results)
                     lines = { }
                 else
                     print "Evaluation error:"
                     print (results[1])
                     lines = { }
                 end
             else
                 print "Can't compile into bytecode:"
                 print (f)
                 lines = { }
             end
         end
      else
         -- If lx has been read entirely, try to read another
         -- line before failing.
         if not reached_eof(lx, ast) then
            print "Can't compile source into AST:"
            print (ast)
            lines = { } 
         end
      end
   end
end