indent style
: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 () { }
}
`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 ()
{ }
}
`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 ()
{ }
}
`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 ()
{ }
}
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
Jargon File Version 4.3.1, 29 JUN 2001 =
Skip to a random entry
Back to Liz's page