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Note in the manual about using '...' as an expression

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Roberto Ierusalimschy 2022-09-08 17:21:02 -03:00
parent cd56f222b7
commit 71bc69c2af
1 changed files with 16 additions and 5 deletions
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manual/manual.of
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@ -1144,7 +1144,9 @@ Lua also accepts @x{hexadecimal constants},
which start with @T{0x} or @T{0X}.
Hexadecimal constants also accept an optional fractional part
plus an optional binary exponent,
marked by a letter @Char{p} or @Char{P}.
marked by a letter @Char{p} or @Char{P} and written in decimal.
(For instance, @T{0x1.fp10} denotes 1984,
which is @M{0x1f / 16} multiplied by @M{2@sp{10}}.)
A numeric constant with a radix point or an exponent
denotes a float;
@ -2291,7 +2293,7 @@ the number of parameters in a call to a non-variadic function
@see{func-def},
the number of variables in a multiple assignment or
a local declaration,
and exactly four for a generic @rw{for} loop.
and exactly four values for a generic @rw{for} loop.
The @def{adjustment} follows these rules:
If there are more values than needed,
the extra values are thrown away;
@ -2310,7 +2312,16 @@ the syntax expects a single expression inside a parenthesized expression;
therefore, adding parentheses around a multires expression
forces it to produce exactly one result.
Here are some examples.
We seldom need to use a vararg expression in a place
where the syntax expects a single expression.
(Usually it is simpler to add a regular parameter before
the variadic part and use that parameter.)
When there is such a need,
we recommend assigning the vararg expression
to a single variable and using that variable
in its place.
Here are some examples of uses of mutlres expressions.
In all cases, when the construction needs
@Q{the n-th result} and there is no such result,
it uses a @nil.
@ -2319,6 +2330,7 @@ print(x, f()) -- prints x and all results from f().
print(x, (f())) -- prints x and the first result from f().
print(f(), x) -- prints the first result from f() and x.
print(1 + f()) -- prints 1 added to the first result from f().
local x = ... -- x gets the first vararg argument.
x,y = ... -- x gets the first vararg argument,
-- y gets the second vararg argument.
x,y,z = w, f() -- x gets w, y gets the first result from f(),
@ -2331,8 +2343,7 @@ x,y,z = f(), g() -- x gets the first result from f(),
-- z gets the second result from g().
x,y,z = (f()) -- x gets the first result from f(), y and z get nil.
return f() -- returns all results from f().
return ... -- returns all received vararg arguments.
return (...) -- returns the first received vararg argument.
return x, ... -- returns x and all received vararg arguments.
return x,y,f() -- returns x, y, and all results from f().
{f()} -- creates a list with all results from f().
{...} -- creates a list with all vararg arguments.