"Userdata subject" feature does not work with Lua 5.1 about lrexlib HOT 9 CLOSED

lua_objlen does indeed push its result on the stack.

As far as I can see, the error here is in the documentation: the phrase "(in Lua >= 5.2)" should be moved to after "userdata".

from lrexlib.

lua_objlen does indeed push its result on the stack.

Both the Lua 5.1 manual and a simple experiment show that it is not true.

As far as I can see, the error here is in the documentation: the phrase "(in Lua >= 5.2)" should be moved to after "userdata".

Do you mean the feature is not supported for Lua 5.1 ?

from lrexlib.

Sorry, I misread the manual. No, I mean that the feature is not supported for userdata in Lua 5.1. In Lua 5.1 a push should be added to put the length on the stack.

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Thanks for adding support for userdata in Lua 5.1, and well done for fixing the error message as well!

Looking at your fix, it seems it now won't work on plain tables in Lua 5.1. Wouldn't it be better simply to lift the restriction in the documentation, and call lua_objlen when the argument is a table without a __len metamethod?

Also, please can you not put patches for different purposes into the same commit.

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Looking at your fix, it seems it now won't work on plain tables in Lua 5.1.

Do you mean that prior to my fix it did work on plain tables in Lua 5.1 ?

Wouldn't it be better simply to lift the restriction in the documentation, and call lua_objlen when the argument is a table without a __len metamethod?

Maybe. Personally I don't need table-subjects such as described above. If you do, please implement it.

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I meant that it would have worked had you simply added a push. The extra fix is small, so it seems hardly worth not making it just to complicate the documentation and make the behaviour different between Lua 5.1 and 5.2. I'll do it.

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Fixed. I also noticed that for Lua 5.2 I could use luaL_len, so the code is now actually slightly shorter than before.

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I meant that it would have worked had you simply added a push. The extra fix is small, so it seems hardly worth not making it just to complicate the documentation and make the behaviour different between Lua 5.1 and 5.2. I'll do it.

Unfortunately I still fail to understand how the length of the table's array part in Lua 5.1 can meaningfully serve as the length of the subject.

The only case that comes to my mind is the table containing an array of single characters, but it seems to be a very specific case not justifying allowing of a table as the subject.

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I'm just trying to make the behaviour the same in Lua 5.1 and 5.2, not decide whether it was sensible, but I see I've failed in any case, since now the Lua 5.1 code doesn't look for a __len metamethod on tables. I've made a change so that it does so.

It would probably have taken less of your time if you'd made this fix, not me!

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