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author | Roberto Ierusalimschy <roberto@inf.puc-rio.br> | 2021-10-11 13:49:13 -0300 |
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committer | Roberto Ierusalimschy <roberto@inf.puc-rio.br> | 2021-10-11 13:49:13 -0300 |
commit | 87a9573b2eb3f1da8e438f92ade994160d930b09 (patch) | |
tree | a935872e61f23c81b430dd867c98329b8782a907 | |
parent | deac067ed39a44c001599c0d15de09872496b2aa (diff) | |
download | lua-github-87a9573b2eb3f1da8e438f92ade994160d930b09.tar.gz |
Documentation
Better explanation about the guaranties of multiple assignment in
the manual.
-rw-r--r-- | ldebug.c | 2 | ||||
-rw-r--r-- | lstrlib.c | 2 | ||||
-rw-r--r-- | lvm.c | 2 | ||||
-rw-r--r-- | manual/manual.of | 12 |
4 files changed, 13 insertions, 5 deletions
@@ -64,7 +64,7 @@ static int getbaseline (const Proto *f, int pc, int *basepc) { } else { int i = cast_uint(pc) / MAXIWTHABS - 1; /* get an estimate */ - /* estimate must be a lower bond of the correct base */ + /* estimate must be a lower bound of the correct base */ lua_assert(i < 0 || (i < f->sizeabslineinfo && f->abslineinfo[i].pc <= pc)); while (i + 1 < f->sizeabslineinfo && pc >= f->abslineinfo[i + 1].pc) @@ -1217,7 +1217,7 @@ static const char *get2digits (const char *s) { /* -** Chech whether a conversion specification is valid. When called, +** Check whether a conversion specification is valid. When called, ** first character in 'form' must be '%' and last character must ** be a valid conversion specifier. 'flags' are the accepted flags; ** 'precision' signals whether to accept a precision. @@ -1109,7 +1109,7 @@ void luaV_finishOp (lua_State *L) { #define ProtectNT(exp) (savepc(L), (exp), updatetrap(ci)) /* -** Protect code that can only raise errors. (That is, it cannnot change +** Protect code that can only raise errors. (That is, it cannot change ** the stack or hooks.) */ #define halfProtect(exp) (savestate(L,ci), (exp)) 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}. |