Re: On the subject of Lua's grammar... --[[ ]]

[Philipp Janda <siffiejoe@...>]

Leandro Candido schrieb:
> Hello all,
>
>
>     As we are in suggestion time, i will make my one. Can you guys add range
> operator? To use like:
>
>     for x in 0..10 do print(x) end or
>     for x in 'A'..'Z' do print(x) end
>
>     Of course the .. need be other letters/signs or we need to change the
> concat operator, because it is "..".
>     Perhaps the best is the word "to":
>
>     for x in 0 to 10 do print(x) end, y = 0 to 10 or y = { 0 to 10 } --
> equal y = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }

What about this:

local function num_range_iterator( state, var1 )
  -- state is the end of the iteration
  var1 = var1 + 1
  if var1 > state then
    return nil
  end
  return var1
end

local function char_range_iterator( state, var1 )
  -- state is the end of the iteration
  local ret = num_range_iterator( state, string.byte( var1 ) )
  return ret and string.char( ret )
end


function range( start, ending )
  local stype, etype = type( start ), type( ending )
  if stype == "string" and etype == "string" then
    return char_range_iterator, string.byte( ending ),
           string.char( string.byte( start )-1 )
  elseif stype == "number" and etype == "number" then
    return num_range_iterator, ending, start-1
  else
    error( "type error in function `range' (strings or numbers expected)" )
  end
end


function from_to( start, ending )
  local tab = {}
  for x in range( start, ending ) do
    table.insert( tab, x )
  end
  return unpack( tab )
end

--------- test -------------------------------------------------------


for x in range( 1, 10 ) do
  print( x )
end

for x in range( 'A', 'Z' ) do
  print( x )
end

local y = { from_to( 1, 10 ) }
for i,j in ipairs( y ) do
  print( i, j )
end




Philipp