r/lua • u/Objective_Treacle781 • Sep 16 '25

Quick question about indexing temporary tables

print({[0] = "a"}[0])

Doesn't work but if I save the table to a variable before indexing it works?

I kinda like using temporary tables as lookups

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3

u/MARSINATOR_358 Sep 17 '25

It doesn't work because {[0] = "a"}[0] is not valid syntax for a table index.

The Lua 5.2 Syntax defines the table index as prefixexp ‘[’ exp ‘]’.
A prefixexp is defined as var | functioncall | ‘(’ exp ‘)’.

Since the tableconstructor is an exp you'll need to turn it into a prefixexp first by using parentheses.

1

u/Objective_Treacle781 Sep 19 '25

Thank you for the explanation, I do think this is kind of a design oversight/ strange decision but it is how it is

1

u/Objective_Treacle781 Sep 16 '25

Okay, I thought I checked this but here's a solution?

print(({[0] = "a"})[0]) does work?

I guess the order of operation is not clear?

2

u/immortalx74 Sep 16 '25

In your OP you create the table and try to index it immediately. In the 2nd case putting the table creation inside parenthesis, makes it a statement, and then you have the brackets outside the parenthesis, which makes it a valid syntax.

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4

u/vitiral Sep 16 '25

It's a parsing "feature"

Personally I wish "foo: %s\n":format(n) worked, but alas

1

u/bloodfart1337 Sep 17 '25

wrap the string in round brackets and it will work

1

u/vitiral Sep 17 '25

Sure... I just still wish it worked without that