metalua/repl.mlua

-------------------------------------------------------------------------------
-- Copyright (c) 2006-2017 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
--
-------------------------------------------------------------------------------

-- Keep these global:
PRINT_AST  = true
LINE_WIDTH = 60
PROMPT     = "M> "
PROMPT2    = ">> "

local pp=require 'metalua.pprint'
local M = { }

mlc = require 'metalua.compiler'.new()

local readline

do -- set readline() to a line reader, either editline otr a default
   local status, editline = pcall(require, 'editline')
   if status then
      local rl_handle = editline.init 'metalua'
      readline = |p| rl_handle:read(p)
   else
      local status, rl = pcall(require, 'readline')
      if status then
         rl.set_options{histfile='~/.metalua_history', keeplines=100, completion=false }
         readline = rl.readline
      else -- neither editline nor readline available
         function readline (p)
            io.write (p)
            io.flush ()
            return io.read '*l'
         end
      end
   end
end

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


function M.run()
    pp.printf ("Metalua, interactive REPLoop.\n"..
            "(c) 2006-2017 <metalua@gmail.com>")
   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 :src_to_lexstream(src)
      success, ast = pcall(mlc.lexstream_to_ast, mlc, lx)
      if success then
          success, f = pcall(mlc.ast_to_function, mlc, ast, '=stdin')
          if success then
              results = { xpcall(f, debug.traceback) }
              success = table.remove (results, 1)
              if success then
                  -- Success!
                  for _, x in ipairs(results) do
                      pp.print(x, {line_max=LINE_WIDTH, metalua_tag=true})
                  end
                  lines = { }
              else
                  print "Evaluation error:"
                  print (results[1])
                  lines = { }
              end
          else
              print "Can't compile into bytecode:"
              print (f)
              lines = { }
          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

return M