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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.
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