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Programming in Lua | ![]() |
Part I. The Language Chapter 1. Getting Started |
1.3 - Some Lexical Conventions
Identifiers in Lua can be any string of letters, digits, and underscores, not beginning with a digit; for instance
i j i10 _ij aSomewhatLongName _INPUTYou should avoid identifiers starting with an underscore followed by one or more uppercase letters (e.g.,
_VERSION
);
they are reserved for special uses in Lua.
Usually,
I reserve the identifier _
(a single underscore)
for a dummy variable.
In Lua, the concept of what is a letter is locale dependent.
Therefore, with a proper locale, you can use variable names such as
índice
or ação
.
However, such names will make your program unsuitable to run in
systems that do not support that locale.
The following words are reserved; we cannot use them as identifiers:
and break do else elseif end false for function if in local nil not or repeat return then true until whileLua is case-sensitive: and is a reserved word, but
And
and AND
are two other different identifiers.
A comment starts anywhere with a double hyphen (--
)
and runs until the end of the line.
Lua also offers block comments,
which start with --[[
and run until the corresponding ]]
.
A common trick,
when we want to comment out a piece of code,
is to write the following:
--[[ print(10) -- no action (comment) --]]Now, if we add a single hyphen to the first line, the code is in again:
---[[ print(10) --> 10 --]]In the first example, the
--
in the last line
is still inside the block comment.
In the second example, the sequence ---[[
does not start
a block comment;
so, the print
is outside comments.
In this case, the last line becomes an independent comment,
as it starts with --
.
Copyright © 2003-2004 Roberto Ierusalimschy. All rights reserved. |
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