Category: Programming

I described in a previous post how I was trying to parse Matlab code. I’ve given up on this endeavour because it is way too much work (we designated a Matlab compiler as a last resort to get everything stand-alone, we will require Matlab in our project to speed up development).

I will however provide my incomplete and broken grammar, as promised. I hope somebody can use this later on as we have dropped the compiler approach completely.

On a side note, we figured out why nobody has a complete grammar for Matlab: its too darn difficult – if you manage to somehow describe the syntax, implementing it (type checking and internal Matlab functions for example) will be a heck of a lot of work. But it can be done, that much is obvious by now.

matlab.g

// Simple grammar for interpreting Matlab files for the MDDP project.
// Written by Berend Dekens
//
// Note: this part of the project is abandoned and will not be completed. The grammar is mostly working in Antlr except
// for some dodgy errors. If you find this usefull and/or manage to fix the parser errors, please let me know so I can
// fix the problems.
//
// Known limitations:
// - No function calls without parenthesis
//	Matlab allows function calls in the form of 'function_name arguments'. This is annoying and thus not allowed.
// - No functions calls (period)
//	Currently we do not allow function calls at all. Implementing this means supporting a large portion of basic
//	Matlab functions and support for declaring new functions across files. This is beyond the scope of this project.
// - No characters or strings in variables
//	Our application is matrices and vectors (integers). Boolean logic is included for the sake of logic blocks and loops.
//
grammar simplematlab;
options {
	output=AST;
	backtrack=true;
 }

// Grammar rules below, start the grammar with a list of statements
statementList
    :   statement (lineSep+ statementList? )?
    ;
    
lineSep
   :    ';' | '\n' | ','
   ;

statement
    :   'if' parExpression statementList ( lineSep 'elseif' parExpression statementList)* ('else' statementList)? lineSep 'end'
    |   'for' Identifier '=' (Identifier | integerLiteral) ':' (Identifier | integerLiteral) (':' (Identifier | integerLiteral))? statementList 'end'
    |   parExpression
    ;

// Expressions
parExpression
    :   '(' expression ')'
    | expression
    ;
    
expression
    :   conditionalOrExpression (assignmentOperator expression)?
    |   '(' conditionalOrExpression (assignmentOperator expression)? ')'
    ;
    
assignmentOperator
    :   '='
    |   '+='
    |   '-='
    |   '*='
    |   '/='
    ;

conditionalOrExpression
    :   conditionalAndExpression ( '||' conditionalAndExpression )*
    ;

conditionalAndExpression
    :   equalityExpression ( '&&' equalityExpression )*
    ;

equalityExpression
    :   relationalExpression ( ('==' | '!=') relationalExpression )*
    ;
    
relationalExpression
    :   additiveExpression ( relationalOp additiveExpression )*
    ;
    
relationalOp
    :   '<='
    |   '>='
    |   '<' 
    |   '>' 
    ;

additiveExpression
    :   multiplicativeExpression ( ('+' | '-') multiplicativeExpression )*
    ;

multiplicativeExpression
    :   unaryExpressionNotPlusMinus ( ( '*' | '/' ) unaryExpressionNotPlusMinus )*
    ;

unaryExpressionNotPlusMinus
    :   '~' unaryExpressionNotPlusMinus
    |   '!' unaryExpressionNotPlusMinus
    |   primary ('++'|'--')?
    ;

primary
    :   parExpression
    |   literal
    |   Identifier (identifierSuffix)?
    ;

literal 
    :   integerLiteral
    |   booleanLiteral
    |   'null'
    ;

integerLiteral
    :   Digit+
    ;

booleanLiteral
    :   'true'
    |   'false'
    ;

identifierSuffix
    :   ('[' ']')+ '.' 'class'
    |   ('[' expression ']')+ // can also be matched by selector, but do here
    |   arguments
    ;

expressionList
    :   expression (',' expression)*
    ;

arguments
    :   '(' expressionList? ')'
    ;

Identifier 
    :   Letter (Letter | Digit)*
    ;

Letter	: 'a'..'z' | 'A'..'Z';
Digit	: '0'..'9';