Re: future of annotations in Lua?

Example of use of an annotation on an empty statement:

a = 1

;(break 'here')

b = 2

here "(break 'here')" is the "break" annotation which may have optional parameters possibly currified, entirely written between parentheses because "break" without them is a core langage statement.

If the annotation is ignored (because there's no debugger using it and the code is just run with a core engine) then it is equivalent to the 3 statements:

a = 1

;

b = 2

with the same empty statement, not necessary here because "1 b" is not a valid currified function call "1(b)" as a constant number is not an object and has no function members, so it is equivalent also to the two separate statements:

a = 1 b=2

Le sam. 8 juin 2019 à 06:04, Philippe Verdy <verdy_p@wanadoo.fr> a écrit :

I see only a single useful case for annotating an empty statement (i.e. just after any single ";" which is always isolated and has no further tokens in any context), it's for emitting some debugger info (or execution tracking logger, or breakpoint) that applies to a reachable point of execution, i.e. between two separate statements that are otherwise not themselves annotated by it.

Le sam. 8 juin 2019 à 05:55, Philippe Verdy <verdy_p@wanadoo.fr> a écrit :
And given the way Lua parses the ";" (only as an empty statement, which is a no-op), adding an annotation just after it would make no sense.
There's no way to unambiguously allow any annotation in Lua at *start* of any statement: it must necessarily be in the middle of the statement before any _expression_ (it can follow an "," separator too, which probably makes sense only if there's something after it which is not the end of the comma-separated list) or just at end of the statement.

Le sam. 8 juin 2019 à 05:44, Philippe Verdy <verdy_p@wanadoo.fr> a écrit :
Yes but Java requires the ";" terminator, so there's no ambiguity when parsing, even if the annotation precedes all the rest of the statement.

In Lua, without the required ";" there will an ambiguity of parsing if the annotation does not follow immediately a statement initial keyword (local, function, for, return, if, then, else, begin...), or a "(" or "[" or "{".

Le ven. 7 juin 2019 à 18:07, Dibyendu Majumdar <mobile@majumdar.org.uk> a écrit :
> There is a big difference between all those syntaxes
[snip]
> They are all prefixed to the whole item to which they
> apply. Following their syntax, we should write '@toclose local x = 1',
> instead of 'local @toclose x = 1'.
>

In Java the annotation precedes the type in a declaration; it being
classed as a type modifier in the grammar (this is one of the uses).
Lua of course doesn't have type declarations therefore annotations
cannot be placed in the same way.

Regards