From 71bc69c2afaf49ab5f54f3443af9ae70dd1fed06 Mon Sep 17 00:00:00 2001 From: Roberto Ierusalimschy Date: Thu, 8 Sep 2022 17:21:02 -0300 Subject: Note in the manual about using '...' as an expression --- manual/manual.of | 21 ++++++++++++++++----- 1 file changed, 16 insertions(+), 5 deletions(-) diff --git a/manual/manual.of b/manual/manual.of index ca7f9933..ade47b20 100644 --- a/manual/manual.of +++ b/manual/manual.of @@ -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. -- cgit v1.2.1