Editing Rebol (section)

===Syntax===
Rebol [[syntax (programming languages)|syntax]] is [[free-form language|free-form]], not requiring specific positioning. However, [[indent style|indentation]] is often used to better convey the structure of the text to human readers.

Syntactic properties of different dialects may differ. The common platform for all Rebol dialects is the ''data exchange dialect''; other dialects are usually derived from it. In addition to being the common platform for all dialects, the ''data exchange dialect'' is directly used to represent data and metadata, populate data structures, send data over Internet, and save them in data storage.

In contrast to programming languages like [[C (programming language)|C]], the ''data exchange dialect'' does not consist of [[declaration (computer science)|declarations]], [[statement (programming)|statement]]s, [[expression (programming)|expressions]] or keywords. A valid ''data exchange dialect'' text stream is a [[tree data structure]] consisting of blocks (the root block is implicit, subblocks are [[delimiter|delimited]] by [[bracket|square brackets]]), parens (delimited by [[bracket|round brackets]]), [[string (computer science)|strings]] (delimited by [[quotation mark|double quotes]] or [[bracket|curly brackets]] suitable for multi-line strings; [[caret notation]] is used for unprintable characters), [[Uniform Resource Locator|URLs]], e-mail addresses, files, paths or other [[scalar (computing)|composite values]]. Unlike [[ALGOL]] [[block (programming)|blocks]], Rebol blocks are composite values similar to quoted [[s-expression]]s in [[Lisp (programming language)|Lisp]]. The fact that code is written in the form of Rebol blocks makes the language [[homoiconicity|homoiconic]].<ref name="OG" />

Blocks as well as parens may contain other composite values (a block may contain subblocks, parens, strings, ...) or [[scalar (computing)|scalar values]] like words, set-words (words suffixed by the [[colon (punctuation)|colon]]), get-words (words prefixed by the colon), lit-words (words prefixed by the [[apostrophe (mark)|apostrophe]]), numbers, money, [[character encoding|characters]], etc., separated by [[whitespace (computer science)|whitespace]]. Special characters are allowed in words, so <code>a+b</code> is a word unlike <code>a + b</code>, which is a sequence of three words separated by spaces.

[[Comment (computer programming)|Comment]]s may appear following the [[semicolon]] until the end of the line. Multi-line comments or comments not ignored by the lexical parser can be written using "ordinary" datatypes like multi-line strings.<ref name="OG" />