Re[2]: Another EU 2.5 suggestion...
- Posted by akusaya at gmx.net
Jan 25, 2004
How if the function is a special function which can return ANY
possible return values, such as float64_to_atom(sequence x) but
modified so that x can be a sequence of 8-element sequences.
NAN, inf, {}, -1 or anything can be considered valid return value.
So for that we need special additional function to detect the error.
Isn't it troublesome?
G> Sometimes I need to return an error code, but my function can return any
G> value, such in the case of a random generator. In this case I use NAN. NAN
G> means Not A Number and is used in C often. It's basically equal to the
G> opposite of zero, which is obviously not a real number.
G> constant -- taken from another post
G> POS_INF = 1.8e+307 * 10,
G> NEG_INF = -POS_INF,
G> NAN = -(POS_INF+NEG_INF)
G> function rand_num()
G> -- generate a random number
G> if (success) then
G> return rand_number
G> else
G> return NAN
G> end if
G> end function
G> procedure test_rand()
G> atom num
G> num = rand_num()
G> if num = NAN then
G> -- ERROR
G> end if
G> end procedure
G> ----- Original Message -----
G> From: "aku saya" <akusaya at gmx.net>
G> To: <EUforum at topica.com>
G> Sent: Sunday, January 25, 2004 1:06 AM
G> 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>
G> 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!
>>
>>
G> TOPICA - Start your own email discussion group. FREE!
|
Not Categorized, Please Help
|
|
