OpenEuphoria

Re: EOF and GOTO and 0th array element

• Posted by Derek Parnell <ddparnell at bigpond.com> Aug 22, 2002
• 517 views

----- Original Message -----
From: "darceman" <darce at ffi.com>
To: "EUforum" <EUforum at topica.com>
Subject: EOF and GOTO and 0th array element


>
> 1. What is the equivalent to a BASIC EOF (end-of-file) marker that I can
> test for?
>
> My current solution for #1 - when inputing a list from a text file with:
>
>      object dd, f1
>
>      dd=get(f1)
>
> At the end of the file, atom(dd) returns a zero, which I use to check
> for an end-of-file marker.  Is there a more "proper" way?

That is the proper way in Euphoria.

>
> 2. At the risk of incurring wrath for writing spaghetti code, is there a
> GOTO equivalent?

Yes and no. Strictly speaking there is no GOTO (thankfully). However, if you
wish to write hard-to-read and hard-to-maintain code, Euphoria still allows
this option. GOTO can be emulated using a state machine concept.

  function routine_1()
      -- do some work
      return 2
  end function

  function routine_2()
      -- do some work
      if xyz then
        return 3
      else
        return 2
      end if
  end function

  function routine_3()
      -- do some work
      if abc then
        return 2
      else
        return 1
      end if
  end function

  function routine_4()
      -- do some work
      if qwerty then
       return 4
      else
          if ytrewq then
               return 1
          end if
          -- do more work
          if ytrewq then
               return 3
          else
               return 0
          end if
      end if
  end function

  -- State Machine --
  x = 0
  state = 1
  while x != -1 do
    x = routine_id(sprintf("routine_%d", state))
    if x != -1 then
      state = call_func(x,{})
    end if
  end while


> 3.  in BASIC an array can be created with 0th (zeroth?) element in any
> dimension, but I don't see how you can do that in a sequence.  Can one
> set up a Euphoric equivalent to such an element in a sequence?

No. Euphoria uses a 1-based index philosophy. The first element in a series
is always 1.

Oh, except for routine_id().

Oh, and open() as well.

> 4.  Nested in a while...end while loop is a for..end for loop.  If a
> test fails in the for..end for loop I want to exit the while..end while
> loop.  However, using exit command in the for..end for loop seems to
> only exit the "for" loop and does not apply to the "while" loop.  Can
> one indicate what to exit if using that command, or (as in the example
> below) do I have to set some condition in the "for" loop to test outside
> of it in order to exit the "while" loop?
>
> .
> .
> somemarker=true
> while 1 do
> .
> .
> --    test values; if fail, exit loop
>       for y=1 to 10 do
>            if test y fails then
>               somemarker=false
>               exit
>            end if
>       end for
>       if somemarker=false then
>           exit
>       end if
> .
> .
> end while
> .
> .
>

This request just keeps on coming up. Euphoria doesn't make it easy for us.
It encourages hard-to-read code in this instance. My "pet" solution is a
form of controlled GOTO.


 somemarker: while 1 do
 .
 .
 --    test values; if fail, exit loop
       for y=1 to 10 do
            if test y fails then
               exit somemarker
            end if
       end for
 .
 .
 end while

----------------
cheers,
Derek Parnell