efun simulate help

[seik...@gmail.com]

undefinedp - determine whether or not a given value is undefined.

 

int undefinedp( mixed arg );

 

Return 1 if `arg' is undefined.  'arg' will be undefined in the following

cases:

 

<DL>

* it is a variable set equal to the return value of a call_other to a

non-existent method (e.g. arg = call_other(obj, "???")).

* it is a variable set equal to the return value of an access of an

element in a mapping that doesn't exist (e.g. arg = map[not_there]).

* it has not yet been initialized.

* it points to a destructed object.

* it is a function (formal) parameter that corresponds to a missing actual argument.

</DL>

I am trying to convert a mudos's mudlib to ldmud

the mudlib use efun undefined a lot how can I simulate it in ldmud 

can anybody help me please thanks very much

[seik...@gmail.com]

when the arg is an element in mapping undefinedp(map[not_here]) returns 1

I can use member(map,not_here),  but there are too many undefinedp(map[not_here]) 

replace them to member(map,not_here) by hand is impossible. so I need a simulate efun

[Michael Conley]

Good to hear you are making the jump to LDMud.

Could you share a MudOS code sample of where you are coming from?  Perhaps that will help understand the use case here.  Also, join up to the new Discord group for LPC.  There is an LDMud channel. Detail here: https://www.reddit.com/r/MUD/comments/mdbbaa/new_discord_server_for_lpc_conversation/.

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[Invisible]

Hi there,

The main problem will be that there is no 'undef' value in LDmud, all variables are implicitly initialized to 0. So a simul_efun that does all you want depending on context is (as far as I know) impossible to implement. Both map[not_there] and map[value_0] return the same "0" (that's why there is a member() function in the first place). So even if you implement a sefun::undefinedp(arg) you will not be able to tell the difference from arg alone.

In some cases like e.g. a destructed object you could have some luck checking the type, but then again a (object)0 for a destructed object is exactly the same as if there never was an object to begin with.

regards
  Invis

--

[seik...@gmail.com]

my = ob->query_entire_dbase();

 

ob->set("default_actions", (: call_other, __FILE__, "query_action" :));

 

if( undefinedp(my["age"]) ) my["age"] = 14;

if (undefinedp(my["str"])) my["str"] = 10 + random(21);

if (undefinedp(my["con"])) my["con"] = 10 + random(21);

if (undefinedp(my["dex"])) my["dex"] = 10 + random(21);

if (undefinedp(my["int"])) my["int"] = 80 - my["str"] - my["con"] - my["dex"];

if (undefinedp(my["per"])) my["per"] = 10 + random(21);

if (undefinedp(my["kar"])) my["kar"] = 10 + random(21);

if (undefinedp(my["sta"]) || my["sta"]==0) my["sta"] = 10 + random(21);

if (undefinedp(my["cps"]) || my["cps"]==0) my["cps"] = 10 + random(21);

if (undefinedp(my["cor"]) || my["cor"]==0) my["cor"] = 10 + random(21);

 this code is used to initialize same properties

I can replace the undefinedp by member but there are too many replace it

hand by hand is impossible

[seik...@gmail.com]

protected nomask  mixed _query( mapping map, string *parts )

{

mixed value;

int i, s;

 

value = map;

s = sizeof( parts );

for( i = 0 ; i < s ; i++ ) {

if( undefinedp( value = value[parts[i]] ) )

break;

if( !mappingp( value ) )

break;

}

return value;

}

and code like this 

在2021年4月9日星期五 UTC+8 下午7:25:14<Tamarindo> 写道：

[Invisible]

Hello again,

At least in this example it looks as if you can just replace undefinedp() with a check for 0.

cu

  Invis

To view this discussion on the web visit https://groups.google.com/d/msgid/ldmud-talk/417a16ed-fd12-44d5-afbc-30f219f99fd4n%40googlegroups.com.

[seik...@gmail.com]

yes you are right

[Zesstra]

On 09.04.21 04:57, seik...@gmail.com wrote:
> undefinedp - determine whether or not a given value is undefined.
> int undefinedp( mixed arg );
> Return 1 if `arg' is undefined.  'arg' will be undefined in the following
> cases:

Invisible already mentioned it - I agree and put it slightly different words:

Technically there is no undefined value in LDMud exposed to the LPC side.
All entities are initialized to a defined value. What people mostly mean by
undefined is "the wizard did not explicitly assign a value (yet)".

However, in many cases that also translates to something like "is the value a
valid one for my purposes".

Therefore in some cases:
If you know the *type* of a variable, you can check whether it contains a
non-zero value of that type, e.g. if the value in a mapping variable is an
actual mapping and not 0.
But this is limited to cases, where the type is known - you don't know it for
the values in mappings, you need member in that case or check for !=0 if 0 is
not a valid value.

tl&dr; In general you need to know something about the context to know whether
a value is "valid" or not and to decide if it counts as "undefined" for you.

In the long run, you will program in a way that takes this into account. ;-)

Bye,
Zesstra
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[Stephan Weinberger]

Though - and I think we talked about this in the past - having a 'none'
or 'undef' value might actually be quite useful sometimes. E.g. when
interacting with databases that have 'NULL' columns.

But I understand that this would likely require major changes to the driver.


cya,
  Invis

[seik...@gmail.com]

I made a sefun like this

int undefinedp(mixed what) 

{

if (what==0) return 1;

return 0;

}

it works

[Karl Tiedt]

That sefun works great until your defined value is actually a zero... 

-Karl Tiedt

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[seik...@gmail.com]

 in that case I have to use member

I can make do with this just for some time

[seik...@gmail.com]

there is no undefined type such as nill/null  I can not tell an undefined 0 from a literal integer 0