OpenEuphoria

1. What's the point of map:map type if load_map() messes it up?

• Posted by euphoric (admin) Sep 12, 2011
• 1247 views

I have

map:map new_game = map:load_map( filename & ".cgm" ) 

but if map:load_map() returns -1 (due to file not existing), I get a type error (type_check failure, new_game is -1). So, the definition of type map is useless! Do I have to resort to this:

map:map new_game 
object maybe_a_map_maybe_not = map:load_map( filename & ".cgm" ) 
 
if map:map( maybe_a_map_maybe_not ) then 
  new_game = maybe_a_map_maybe_not 
else 
  msg( "No saved games. Start a new game." ) 
end if 

Maybe if load_map() fails we can return an empty map (which is not accurate, but better than failing)? or in the type definition we include the possibility that map:map can be -1?

3. Re: What's the point of map:map type if load_map() messes it up?

• Posted by euphoric (admin) Sep 12, 2011
• 1263 views

map:map new_game = map:load_map( filename & ".cgm" ) 

It's funny you mention it, because I don't think I ever turn type checking off. :) Do translated programs automatically have type checking off?

Anyway, I've added a check to make sure the file exists.

Thank you!

5. Re: What's the point of map:map type if load_map() messes it up?

• Posted by jeremy (admin) Sep 12, 2011
• 1258 views

I wonder if in cases like this the map type shouldn't support an error condition.

public type map(object obj_p) 
    if integer(obj_p) then return 1 end if 
    ... 
end if 
 
public function is_error(object obj_p) 
    if integer(obj_p) then return obj_p end if 
    return 0 
end function 

That would allow for nicer code:

map my_map = map:load_map("file.txt") 
if map:is_error(my_map) then 
    printf(1, "Map error: %d\n", { map:error_code(my_map) }) 
    abort(1) 
end if 

Thus, it allows type checking during development and promotes error checking.

Alternatively, you could write a wrapper function

function load_or_empty_map(sequence f) 
    object o = map:load_map(f) 
    if atom(o) then 
        log:warning("map not found") 
        o = map:new() 
    end if 
    return o 
end function 

Not sure that would solve your problem though, because what happens if it is an empty map? Is that a fail condition?

Another option is to have another type:

public type map_or_error(object obj_p) 
    if atom(obj_p) return 1 end if 
    return map:map(obj_p) 
end type 
 
map_or_error m = map:load_map("file.txt") 
if atom(m) then 
    -- handle error 
end if 
 
-- m is a map 

Jeremy

7. Re: What's the point of map:map type if load_map() messes it up?

• Posted by DerekParnell (admin) Sep 12, 2011
• 1236 views

I wonder if we should wait until we get a comprehensive solution, such as exceptions built into the language.

9. Re: What's the point of map:map type if load_map() messes it up?

• Posted by jimcbrown (admin) Sep 14, 2011
• 1087 views

I thought exceptions were being added in 5.0

Unless we have plans for implementation exceptions immediately, we need some kind of compromise.

I came up with a very generic, if somewhat unwieldy, way to deal with this:

-- generic type test 
public function gtt(object value, integer routine_id_of_type, integer routine_id_of_error_handling_procedure, object default_valid_value) 
	if not call_func(routine_id_of_type, {value}) then 
		if routine_id_of_error_handing_procedure >= 0 then 
			call_proc(routine_id_of_error_handling_procedure, {value}) 
			--return call_func(routine_id_of_error_handling_function, {value}) 
		end if 
		return default_valid_value 
	end if 
end function 
 
--public constant NO_ROUTINE_ID = -2 
map:map t = ggt(map:load_map("file"), routine_id("map:map"), NO_ROUTINE_ID, empty_map)