ETrice/GSoC/2012/GACL

Generic Action Code Language (GACL)

GACL is the language to describe the Detail Code for execution of ROOM Models in eTrice plugin . GACL aims at dealing with all features commonly available in imperative languages , especially Java , C/C++ . It will act as complement of current version of eTrice which uses code written in target language stored in a string as execution code . GACL would make user able to write execution code independent of target language .

Development Details and Core Information

Features of GACL

• Variable Declarations ( with optional initializers ) and Function Declaration .
• Comparison & arithmetic expressions .
• Basic types , and user defined types .
• If-else blocks and ladders .
• For , while , for each , enhanched for each .
• Support for iterators (that can be used by for each loops ) .
• Function Calls with arguments & diff types i.e. ref/value/address .
• type checking and as much as possible implicit type casting .
• Casts corresponding to static casts in C .

Thoughts on Syntax & Grammar

Although syntax for GACL is still being designed but here are few thought regarding syntax .

TypeDeclaration

Syntax

 type prt type xyz int
 type pqr { int Hello , char ch , prt p , op f1:int() , op f2:char(char,char) }    type pqr' {pqr e1}
 prt {pqr p};

Action

• Declares a type prt ended with whitespace
• Creates a type xyz same as int where type declaration ended with newline
• Creates a type pqr representing a structure rather class with abstracted elements Hello of type int , ch of char , p of type prt and f1 and f2 of type op i.e. Operations . f1 and f2 can take use of their arguments and also other elements of pqr i.e. Hello and ch in this case and ended with a tab .
• Creates a type pqr' with e1 of pqr abstracted in it ended with newline
• Creates prt declared already with p of type pqr abstracted in it ended with semicolon

Grammar

 { "type" typename [ existingtype | "{" TypeCode "}" ] [";" | "\n" | "\t" | " "] } | {typename typecode}

VariableDeclaration

Syntax

 int x
 y;
 y=2    x=y
 x=x+4 y=y+0.5

Action

• Declares a variable x of type int , declaration ended with newline .
• Declares a variable y , declaration ended with semicolon .
• Instantiate a variable y with value of 2 (2 as expression) (Value of 2 would be type checked and its type would be assigned to y unless and until there exists another assignment of y with type which can be type casted into type of value) instantiation ended with "\t"
• Instantiate a variable x with value of expression y which is currently 2 .
• Assigns variable x with value of expression x+4 which would be solved and accordingly value of x would be assigned
• Assigns variable y with value of expression x+0.5 which would be solved and accordingly value of y would be assigned (In this case type of y would be changed actually while writing it would be statically analyzed whether we need to type cast y and is it possible to type cast ) .

Grammar

 [ type ] varname [ "=" { varname2 | Expression } ] { ";" | "\n" | "\t" | " "}

Expression

Syntax

 x+4
 y==z

Action

• First One is an example of arithmetic expression and would have same action as it have for an arithmetic expression .
• Second One is an example of Logical expression and it would have same action as it have for a logical expression .

Grammar

 { ArithmeticExpression | LogicalExpression }

ArithmeticExpression

Syntax

 { Expression { "+" | "-" | "*" | "/" | "**" | "^" | "%" | "div" } Expression } 
| {Expression { "++" | "--" } } | { { "++" | "--" } Expression }

LogicalExpression

Grammar

 { Expression { "<" | "<=" | "==" | ">" | ">=" | "|" | "||" | "&" | "&&" | "^" } Expression }

Statement

Grammar

 { TypeDeclaration | VariableDeclaration | Expression }

StatementList

Grammar

 { Empty | Statement { { "\n" | "\t" | " "}* } Statementlist }

Program

Grammar

 {  Statementlist }

Disambiguation

The syntax used to specify the grammar in brief is

• Things written in double quotes ("") stand as string written in source .
• Content inside braces ({}) represents required content .
• Content inside square brackets ([]) represents optional content .
• Everything rest is either terminal or non-terminals .
• Empty and statement list need a more thought to be done . We would surely finally come up with a better solution .

Project Proposal

Click Here to see the project proposal at gsoc's website .

Click Here to see the project proposal in my github repository .

Useful Links

• eTrice Documentation Page
• Xtext Home Page
• eTrice Home Page
• My Github profile page
• eTrice Forums page