The Arx Syntax and Semantics

The Arx language has a mainstream syntax comparable to the syntax of languages as C, Pascal, Matlab, or VHDL. The most deviant syntax feature is maybe that no semicolons are used at the end of statements.

Arx is case sensitive. All keywords should be written in lower case. Identifiers can have upper and lower case characters. It is, however, not recommended to rely on case for distinguishing identifiers. VHDL, for example, is not case sensitive which will cause identifiers that only differ in case to become identical after code generation.

A simple notation is used to describe the Arx syntax. In principle, the syntax elements (keywords, punctuation, etc.) themselves are directly presented. Elements that do not belong to the language are enclosed in angle brackets < and >. So:

bitvector(<n>)

is used to indicate that the vector length <n> is part of the bitvector. For real Arx code <n> should be replaced by an integer or an expression that evaluates to an integer:

bitvector(32)

or:

bitvector(word_length-1)

An optional syntax element is indicated by enclosing it in the brace pairs -{ and }-. The repetition of some syntax element by one or more times is indicated by putting that element between the special brace pairs +{ and }+. The brace pairs *{ and }* are used for a repetition of zero or more times. So, the syntax description:

variable
  +{ <name> *{, <name>}* : <type> }+

indicates that the following fragment of code is valid:

variable
  a, b: integer
  c: real

Arx specifies components, which are comparable to modules in Verilog or entity-architecture combinations in VHDL. Readers new to Arx are recommended to visit the component page and follow from there the links to the other language elements.

The list below gives direct access to important main topics relevant for learning the Arx syntax and semantics:

• The component
• Declarations
• Statements
• Expressions and operators
• Data types
• Instantiation and hierarchical descriptions
• Function definition and function call