What does :: (double-colon) mean before an assignment in lua?

Question

I am currently looking through the first page of documentation for LUA and noticed that every assignment appears as var ::= Name, however I could not find any reference to the syntax of ::= itself. The documentation goes over the structuring of an assignment but glosses over these symbols. What I want to know is if every assignment requires the :: before the actual assignment operator, and, if so, why is it structured this way and not just a plain =?

Here is the complete syntax of Lua in extended BNF (c)Lua manual. See BNF description — Egor Skriptunoff
– Egor Skriptunoff, Commented May 24, 2021 at 0:04

Nicol Bolas · Accepted Answer · 2021-05-24 00:09:58Z

4

What you're seeing is not Lua code, but a fragment of the grammar of the Lua language, as defined in Backus-Naur Form. The ::= operator is part of BNF.

answered May 24, 2021 at 0:09

Nicol Bolas

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Silent Pants Over a year ago

Thanks for clearing that up! I wish there was some way to tell what are BNF symbols and what is not without knowing all the symbols in the first place. Perhaps they should bold/italicize or something.

Neel Sandell · Accepted Answer · 2021-08-29 02:40:09Z

-1

It's the assignment operator - typically used in formal grammars.

answered Aug 29, 2021 at 2:40

Neel Sandell

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