Dao Language Specifications 1.1 (Draft: Alpha 1) - Introduction

Introduction Lexical Structures Variables, Values and Types Expressions Statements Functions Classes Modules and Name Spaces

1 Introduction

Top

Notations Embedded Tests

This documentation will provide a detailed specification of the Dao programming language. The main purpose is two fold: (1) to produce a guidline for the implementation that shall lead to Dao 1.1; (2) to provide some essential materials for people who want to go deep into the language.

So this specification does NOT conform exactly to what is available in the current release (1.0), it may contain specifications that are going to be changed or added in the implementation for the next release. But this documentation will mark such places clearly. The version code in the title, Draft: Alpha 1 , does not corresponding to the version number of the Dao language and releases, it is merely a way to indicate the progress of the preparation of this specification.

1.1 Notations

Top

Syntax definition: A ::= B , A is defined as B , which can be a descriptive sentence or a combination of the following definition items,

1. Descriptive: " description "
2. Alternative: S | Y
3. Optional: [ S ]
4. Grouping: ( S )
5. Repeating: S * or S +
   • * : zero or more times;
   • + : once or more times;

Examples,

• ( S | Y )+ represents all the possible sequences composed of S and Y: S; Y; SY; YS; SSY ...
• S ( Y | N ) T represents: S Y T or S N T .

The following notation is used in a few places (mainly character class definition):

1. Conditional definition: A ::= S & C(S)
   A is defined as S where C(S) is true.

1.2 Embedded Tests

Top

Testing codes are embedded in this specification using the SDML tag demo , which can contain a block of Dao codes and the expected output of the codes. The expected output is separated from the source codes by [[output]] . When this document is processed by the tool that handles this documentation format, the codes inside the demo block will be executed and the output will be compared with the expected ones to check if the test is passed.

2 Lexical Structures

Top

3 Variables, Values and Types

Top

4 Expressions

Top

5 Statements

Top

6 Functions

Top

7 Classes

Top

8 Modules and Name Spaces

Top