Special notations are used in this specification to denote Chapel code and to denote Chapel syntax.
Chapel code is represented with a fixed-width font where keywords are bold and comments are italicized.
Example.for i in D do // iterate over domain D writeln(i); // output indices in D
Chapel syntax is represented with standard syntax notation in which productions define the syntax of the language. A production is defined in terms of non-terminal (italicized) and terminal (non-italicized) symbols. The complete syntax defines all of the non-terminal symbols in terms of one another and terminal symbols.
A definition of a non-terminal symbol is a multi-line construct. The first line shows the name of the non-terminal that is being defined followed by a colon. The next lines before an empty line define the alternative productions to define the non-terminal.
The productionbool-literal: 'true' 'false'
bool-literalto be either the symbol
In the event that a single line of a definition needs to break across multiple lines of text, more indentation is used to indicate that it is a continuation of the same alternative production.
As a short-hand for cases where there are many alternatives that define one symbol, the first line of the definition of the non-terminal may be followed by “one of” to indicate that the single line in the production defines alternatives for each symbol.
The productionunary-operator: one of + - ~ !
is equivalent tounary-operator: + - ~ !
As a short-hand to indicate an optional symbol in the definition of a production, the subscript “opt” is suffixed to the symbol.
The productionformal: formal-tag identifier formal-type[OPT] default-expression[OPT]
is equivalent toformal: formal-tag identifier formal-type default-expression formal-tag identifier formal-type formal-tag identifier default-expression formal-tag identifier