indent style n.
[C, C++, and Java programmers] The rules one uses to indent
code in a readable fashion. There are four major C indent styles,
described below; all have the aim of making it easier for the
reader to visually track the scope of control constructs. They
have been inherited by C++ and Java, which have C-like syntaxes.
The significant variable is the placement of { and
} with respect to the statement(s) they enclose and
to the guard or controlling statement (if,
else, for, while, or
do) on the block, if any.
`K&R style' -- Named after Kernighan & Ritchie,
because the examples in K&R are
formatted this way. Also called `kernel style' because the Unix
kernel is written in it, and the `One True Brace Style' (abbrev.
1TBS) by its partisans. In C code, the body is typically indented
by eight spaces (or one tab) per level, as shown here. Four
spaces are occasionally seen in C, but in C++ and Java four tends
to be the rule rather than the exception.
if (<cond>) {
<body>
}
`Allman style' -- Named for Eric Allman, a Berkeley hacker who
wrote a lot of the BSD utilities in it (it is sometimes called
`BSD style'). Resembles normal indent style in Pascal and Algol.
It is the only style other than K&R in widespread use among
Java programmers. Basic indent per level shown here is eight
spaces, but four (or sometimes three) spaces are generally
preferred by C++ and Java programmers.
if (<cond>)
{
<body>
}
`Whitesmiths style' -- popularized by the examples that came
with Whitesmiths C, an early commercial C compiler. Basic indent
per level shown here is eight spaces, but four spaces are
occasionally seen.
if (<cond>)
{
<body>
}
`GNU style' -- Used throughout GNU EMACS and the Free Software
Foundation code, and just about nowhere else. Indents are always
four spaces per level, with { and }
halfway between the outer and inner indent levels.
if (<cond>)
{
<body>
}
Surveys have shown the Allman and Whitesmiths styles to be the
most common, with about equal mind shares. K&R/1TBS used to
be nearly universal, but is now much less common in C (the
opening brace tends to get lost against the right paren of the
guard part in an if or while, which is
a Bad Thing). Defenders of 1TBS
argue that any putative gain in readability is less important
than their style's relative economy with vertical space, which
enables one to see more code on one's screen at once.
The Java Language Specification legislates not only the
capitalization of identifiers, but where nouns, adjectives, and
verbs should be in method, class, interface, and variable names
(section 6.8). While the specification stops short of also
standardizing on a bracing style, all source code originating
from Sun Laboratories uses the K&R style. This has set a
precedent for Java programmers, which most follow.
Doubtless these issues will continue to be the subject of
holy wars.