OpenEuphoria

Re: Another EU 2.5 suggestion...

• Posted by "Greg Haberek" <g.haberek at comcast.net> Jan 25, 2004
• 512 views

Sometimes I need to return an error code, but my function can return any
value, such in the case of a random generator. In this case I use NAN. NAN
means Not A Number and is used in C often. It's basically equal to the
opposite of zero, which is obviously not a real number.

constant        -- taken from another post
   POS_INF = 1.8e+307 * 10,
   NEG_INF = -POS_INF,
   NAN     = -(POS_INF+NEG_INF)

function rand_num()
    -- generate a random number
    if (success) then
        return rand_number
    else
        return NAN
    end if
end function

procedure test_rand()
atom num
    num = rand_num()
    if num = NAN then
        -- ERROR
    end if
end procedure


----- Original Message -----
From: "aku saya" <akusaya at gmx.net>
To: <EUforum at topica.com>
Sent: Sunday, January 25, 2004 1:06 AM
Subject: Re: Another EU 2.5 suggestion...


>
>
> After reading many posts about the eval() function, I want to post my
> opinion, that eval() will not be suitable for euphoria, because
> euphoria can be translated and compiled, not just interpreted. Eval()
> needs interpreter. So I think there will never be an eval() function
> in euphoria.
>
> However I really want a method to set and detect unassigned value in
> euphoria. This function
>
>   constant ERROR = -1
>
>   function generate_random()
>       -- generate a random number
>       if (success) then
>           return the_number
>       else
>           return ERROR  -- failed to generate
>       end if
>   end function
>
>   procedure main()
>       object x  x = generate_random()
>       if x = ERROR then
>           puts(1, "error occured")
>       end if
>   end procedure
>
> would be able to be replaced by:
>
>   function generate_random()
>       -- generate a random number
>       if (success) then
>           return the_number
>       else
>           return no_value()  -- failed to generate
>                  ^^^^^^^^^
>                  built-in function that returns unassigned
>       end if
>   end function
>
>   procedure main()
>       object x  x = generate_random()
>       if unassigned(x) then
>           puts(1, "error occured")
>       end if
>   end procedure
>
> For a function that returns all possible value it will be very useful
> to differentiate special return value.
>
>
> C> I would like to be able to set the value of a variable like this:
> C> integer
> C>
some_extremly_long_variable_name=82,another_extremly_long_variable_name=45
>
> C> Instead of:
> C> integer
> C> some_extremly_long_variable_name,another_extremly_long_variable_name
> C> some_extremly_long_variable_name=82
> C> another_extremly_long_variable_name=45
>
> C> This would be much easeyer, especilly with long variable names.
> C> This is already used in constants, so why not with regular variables?
>
> C> And I would also REALLY like my other suggestions included:
>
> C> "eval()" commands/crash callbacks/ect. for Euphoria 2.5?
>
> C> Some of the following is missing from Euphoria and would be very
> C> helpful to me and many other programmers. I would like to see this in
> C> Eu 2.5. Please take these into consideration.
>
>
> C> "eval()" commands:
> C> I would really like to see a way to do an "eval()" type command.
> C> Many other languages have something like this.
>
> C> eval(sequence eval_commands,integer global_type,integer crash)
> C> eval_commands is a sequence of commands
> C> global_type is:
> C> 0-No routines/varibles (even global) exist in main program
> C> 1-Only routines/varibles declared as global exist in main program
> C> 2-All routines/varibles exist in main program
>
> C> if crash is true, if it encounters an error (like 1/0) than the
> C> program dies with (or a crash routine, see below) ex.err, otherwise, it
> C> returns an error
> C> code(like 5 for divide by 0,see below)
>
>
> C> Example:
> C> integer a,global_type
> C> sequence eval_commands
>
> C> eval_commands="
> C> include incl_file.e--should allow including(This could be used
> C> --instead of complex "dynamic includeing" libraries)
> C> if a then
> C> ?a
> C> end if"
>
> C> a=7
> C> var_type=1
>
> C> ?eval(eval_commands,global_type,0)
> C> Displays:
> C> 7(value of a)
> C> 0(eval encountered no errors)
>
> C> ____________________________________________________________
> C> Crash callback
> C> A way to setup a callback function would allow programs to save user
> C> data before exiting
> C> with ex.err
>
> C> set_crash(integer routine_id)
> C> routine_id is the routine id of the function
> C> it calls the function with an error code(like 5 for divide by 0),
> C> a sequence with info about the error(like a line #, invalid subscript,
> C> ect.)
> C> and a text string with the complete text error message(
> C> "test.ex:3
> C> attempt to divide by 0")
>
> C> if the function returns -1, ignore the error
>
> C> Example:
> C> function oncrash(integer err_code,sequence info,sequence msg)
> C> if err_code=34 then--this error can be ignored in this program
> C> return -1
> C> end if
> C> save_all_important_data()
> C> return 0
> C> end function
> C> set_crash(routine_id("oncrash"))
>
> C> _________________________________________________
>
>
> C> TOPICA - Start your own email discussion group. FREE!
>
>
>
> TOPICA - Start your own email discussion group. FREE!
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