From 87a9573b2eb3f1da8e438f92ade994160d930b09 Mon Sep 17 00:00:00 2001 From: Roberto Ierusalimschy Date: Mon, 11 Oct 2021 13:49:13 -0300 Subject: Documentation Better explanation about the guaranties of multiple assignment in the manual. --- manual/manual.of | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) (limited to 'manual') diff --git a/manual/manual.of b/manual/manual.of index ea9a0302..9e0b8835 100644 --- a/manual/manual.of +++ b/manual/manual.of @@ -1346,8 +1346,10 @@ then all values returned by that call enter the list of values, before the adjustment (except when the call is enclosed in parentheses; see @See{expressions}). -The assignment statement first evaluates all its expressions -and only then the assignments are performed. +If a variable is both assigned and read +inside a multiple assignment, +Lua ensures all reads get the value of the variable +before the assignment. Thus the code @verbatim{ i = 3 @@ -1367,6 +1369,12 @@ x, y, z = y, z, x } cyclically permutes the values of @id{x}, @id{y}, and @id{z}. +Note that this guarantee covers only accesses +syntactically inside the assignment statement. +If a function or a metamethod called during the assignment +changes the value of a variable, +Lua gives no guarantees about the order of that access. + An assignment to a global name @T{x = val} is equivalent to the assignment @T{_ENV.x = val} @see{globalenv}. -- cgit v1.2.3-55-g6feb