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Variable attributes can prefix name list

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In this format, the attribute applies to all names in the list;
e.g. "global<const> print, require, math".
This commit is contained in:
Roberto Ierusalimschy
2025-05-18 11:43:43 -03:00
parent f2c1531e6c
commit abbae57c78
15 changed files with 84 additions and 60 deletions
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30
manual/manual.of
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@@ -1651,43 +1651,47 @@ Function calls are explained in @See{functioncall}.
Local and global variables can be declared anywhere inside a block.
The declaration for locals can include an initialization:
@Produc{
@producname{stat}@producbody{@Rw{local} attnamelist @bnfopt{@bnfter{=} explist}}
@producname{stat}@producbody{@Rw{local}
attnamelist @bnfopt{@bnfter{=} explist}}
@producname{stat}@producbody{@Rw{global} attnamelist}
@producname{attnamelist}@producbody{
@bnfNter{Name} @bnfopt{attrib}
@bnfrep{@bnfter{,} @bnfNter{Name} @bnfopt{attrib}}}
}
If present, an initial assignment has the same semantics
of a multiple assignment @see{assignment}.
Otherwise, all local variables are initialized with @nil.
Each variable name may be postfixed by an attribute
(a name between angle brackets):
The list of names may be prefixed by an attribute
(a name between angle brackets)
and each variable name may be postfixed by an attribute:
@Produc{
@producname{attnamelist}@producbody{
@bnfopt{attrib} @bnfNter{Name} @bnfopt{attrib}
@bnfrep{@bnfter{,} @bnfNter{Name} @bnfopt{attrib}}}
@producname{attrib}@producbody{@bnfter{<} @bnfNter{Name} @bnfter{>}}
}
A prefixed attribute applies to all names in the list;
a postfixed attribute applies to its particular name.
There are two possible attributes:
@id{const}, which declares a @emph{constant} or @emph{read-only} variable,
@index{constant variable}
that is, a variable that cannot be used as the left-hand side of an
assignment,
and @id{close}, which declares a to-be-closed variable @see{to-be-closed}.
A list of variables can contain at most one to-be-closed variable.
Only local variables can have the @id{close} attribute.
A list of variables can contain at most one to-be-closed variable.
Lua offers also a collective declaration for global variables:
@Produc{
@producname{stat}@producbody{@Rw{global} @bnfter{*} @bnfopt{attrib}}
@producname{stat}@producbody{@Rw{global} @bnfopt{attrib} @bnfter{*}}
}
This special form implicitly declares
as globals all names not explicitly declared previously.
In particular,
@T{global * <const>} implicitly declares
@T{global<const> *} implicitly declares
as read-only globals all names not explicitly declared previously;
see the following example:
@verbatim{
global X
global * <const>
global<const> *
print(math.pi) -- Ok, 'print' and 'math' are read-only
X = 1 -- Ok, declared as read-write
Y = 1 -- Error, Y is read-only
@@ -1700,7 +1704,7 @@ the scope of any other @Rw{global} declaration.
Therefore, a program that does not use global declarations
or start with @T{global *}
has free read-write access to any global;
a program that starts with @T{global * <const>}
a program that starts with @T{global<const> *}
has free read-only access to any global;
and a program that starts with any other global declaration
(e.g., @T{global none}) can only refer to declared variables.
@@ -9620,11 +9624,11 @@ and @bnfNter{LiteralString}, see @See{lexical}.)
@OrNL @Rw{global} @Rw{function} @bnfNter{Name} funcbody
@OrNL @Rw{local} attnamelist @bnfopt{@bnfter{=} explist}
@OrNL @Rw{global} attnamelist
@OrNL @Rw{global} @bnfter{*} @bnfopt{attrib}
@OrNL @Rw{global} @bnfopt{attrib} @bnfter{*}
}
@producname{attnamelist}@producbody{
@bnfNter{Name} @bnfopt{attrib}
@bnfopt{attrib} @bnfNter{Name} @bnfopt{attrib}
@bnfrep{@bnfter{,} @bnfNter{Name} @bnfopt{attrib}}}
@producname{attrib}@producbody{@bnfter{<} @bnfNter{Name} @bnfter{>}}