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Re: DSPic FORTH

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Hugh Aguilar wrote:

> On Jan 14, 3:09 pm, rickman <gnu...@gmail.com> wrote:
> > Care to clue me in as to why closures are so important?
> 
> No, I wouldn't care to --- read any novice-level book on programming
> any modern language for this information.

A couple of simple closure examples in Lua.


--  A function that returns a closure.
function make_stepper()
  local i = 0
  return function () i = i + 1  return i  end
end

function make_matrix (height, width, func)
  mat = {}
  for row = 1, height do
    mat[row] = {}
    for col = 1, width do
      mat[row][col] = func(row,col)
    end
  end
  return mat
end

function print_matrix (mat)
  for _, row in ipairs(mat) do
    for _, x in ipairs(row) do  io.write(string.format("%3d",x))  end
    print()
  end
end

print_matrix( make_matrix( 5, 5, function(y,x) return y*x end ))
 ===>
  1  2  3  4  5
  2  4  6  8 10
  3  6  9 12 15
  4  8 12 16 20
  5 10 15 20 25

print_matrix( make_matrix( 4, 5, make_stepper() ))
 ===>
  1  2  3  4  5
  6  7  8  9 10
 11 12 13 14 15
 16 17 18 19 20




-- A function that returns a closure.
function make_counter ()
  local cnt = 0
  return
    function (arg)
      if arg then
        return cnt
      else
        cnt = cnt + 1
      end
    end
end

counts = {string=make_counter(), number=make_counter(), table=make_counter()}

for _, x in ipairs({1,2,3,4,5,"a","b",'c',{},{}}) do
  counts[ type(x) ]()
end

for key, val in pairs( counts ) do
  print( val('report') .. " " .. key .. 's' )
end

 ===>

5 numbers
3 strings
2 tables

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Re: DSPic FORTH "WJ" <w_a_x_man@yahoo.com> - 2013-05-11 11:32 +0000

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