[antlr-interest] Evaluation boolean expressions

[Tarun Khanna]

Hi,

Here is the changed grammar. Seems to work fine. I hope you'll notice the 
changes...

The first one is in atom, atom: LPAREN logicalOrExpression RPAREN

Then in the TreeParser, I have added a new rule lexpr.

Parse the tree using logicalOrExpression as the starting point. Then use the 
lexpr to walk the tree.

-----------------------------
class ExprParser extends Parser;

options {

buildAST = true;

defaultErrorHandler = false;

}

logicalOrExpression: logicalAndExpression (OR^ logicalAndExpression)*

;

logicalAndExpression: bexpr (AND^ bexpr)*

;

bexpr: expr ((EQUALS^|NOT_EQUALS^|GT^|GTE^|LT^|LTE^) expr)*

;

expr: mexpr ((PLUS^|MINUS^) mexpr)*

;

mexpr

: atom ((MULT^|DIV^) atom)*

;

atom: INT

| LPAREN! logicalOrExpression RPAREN!

// | LPAREN! logicalOrExpression RPAREN!

;

class ExprLexer extends Lexer;

options {

k = 2; // two characters of lookahead

}

/* Integers */

INT : ('0'..'9')+ ;

/* Ignored characters */

WS : ( ' '

| '\r' '\n'

| '\n'

| '\t'

)

{$setType(Token.SKIP);}

;

/* Logical operators */

OR : "OR";

AND : "AND";

/* Comparison operators */

EQUALS : "==";

NOT_EQUALS : "<>";

GT : '>';

GTE : ">=";

LT : '<';

LTE : "<=";

/* Arithmetic operators */

PLUS : '+';

MINUS : '-';

MULT : '*';

DIV : '/';

/* Parentheses */

LPAREN : '(';

RPAREN : ')';

class ExprTreeParser extends TreeParser;

options {

importVocab=ExprParser;

}

expr returns [int r=0] { int a,b;}

: #(PLUS a=expr b=expr) { r = a + b;}

| #(MINUS a=expr b=expr) { r = a - b; }

| #(MULT a=expr b=expr) { r = a * b; }

| #(DIV a=expr b=expr) { r = a / b; }


| i:INT {r = (int)Integer.parseInt(i.getText());}

;

bexpr returns [boolean r=false] { int a,b; }

: #(EQUALS a=expr b=expr) {r = (a == b);}

| #(NOT_EQUALS a=expr b=expr) {r = (a != b);}

| #(GT a=expr b=expr) {r = (a > b);}

| #(GTE a=expr b=expr) {r = (a >= b);}

| #(LT a=expr b=expr) {r = (a < b);}

| #(LTE a=expr b=expr) {r = (a <= b);}

;

lexpr returns [boolean r= false] {boolean a, b;}
: #(OR a=bexpr b=bexpr) { r = a || b; }

| #(AND a=bexpr b=bexpr) { r = a && b; }

;




On 7/26/05, Xavier Benveniste <xavier.benveniste at free.fr> wrote:
> 
> Hi,
>  I (hardly) succeeded in building a very simple int calculator.
> Then, I succeeded in building an int 'equality' evaluator :
> for instance, if I enter :
> 5+(4*3) > 10 + 9
> 
> I have the following result :
> 
> ( > ( + 5 ( * 4 3 ) ) ( + 10 9 ) )
> 
> false
> 
> So far, so good.
> Now, what I'm trying to do is to evaluate expression like :
> (4 + (5*2) > 15) OR (4>1).
> But, here I'm stuck.
>  You 'll find below the grammar I wrote.
> I'm sure it's pretty straightforward but I can't manage to achieve it.
> If any ANTLR's guru could help me.
> Thanks.
> * 
> 
> class
> * ExprParser *extends* Parser;* 
> 
> options
> * { 
> 
> buildAST = 
> *true*; 
> 
> defaultErrorHandler = 
> *false*; 
> 
> }
> 
> //logicalOrExpression: logicalAndExpression (OR^ logicalAndExpression)*
> 
> // ;
> 
> //logicalAndExpression: bexpr (AND^ bexpr)*
> 
> // ;
> 
> bexpr: expr ((EQUALS^|NOT_EQUALS^|GT^|GTE^|LT^|LTE^) expr)*
> 
> ;
> 
> expr: mexpr ((PLUS^|MINUS^) mexpr)*
> 
> ;
> 
> mexpr
> 
> : atom ((MULT^|DIV^) atom)*
> 
> ;
> 
> atom: INT
> 
> | LPAREN! expr RPAREN!
> 
> // | LPAREN! logicalOrExpression RPAREN!
> 
> ;
> * 
> 
> class
> * ExprLexer *extends* Lexer;* 
> 
> options
> * { 
> 
> k = 2; 
> // two characters of lookahead 
> 
> }
> 
> /* Integers */
> 
> INT : (
> '0'..'9')+ ; 
> 
> /* Ignored characters */
> 
> WS : ( 
> ' ' 
> 
> | 
> '\r' '\n' 
> 
> | 
> '\n' 
> 
> | 
> '\t' 
> 
> )
> 
> {$setType(Token.SKIP);}
> 
> ;
> 
> /* Logical operators */
> 
> OR : 
> "OR"; 
> 
> AND : 
> "AND"; 
> 
> /* Comparison operators */
> 
> EQUALS : 
> "=="; 
> 
> NOT_EQUALS : 
> "<>"; 
> 
> GT : 
> '>'; 
> 
> GTE : 
> ">="; 
> 
> LT : 
> '<'; 
> 
> LTE : 
> "<="; 
> 
> /* Arithmetic operators */
> 
> PLUS : 
> '+'; 
> 
> MINUS : 
> '-'; 
> 
> MULT : 
> '*'; 
> 
> DIV : 
> '/'; 
> 
> /* Parentheses */
> 
> LPAREN : 
> '('; 
> 
> RPAREN : 
> ')';* 
> 
> class
> * ExprTreeParser *extends* TreeParser;* 
> 
> options
> * { 
> 
> importVocab=ExprParser;
> 
> }
> 
> expr 
> *returns* [*int* r=0] { *int* a,b;} 
> 
> : #(PLUS a=expr b=expr) { r = a + b;}
> 
> | #(MINUS a=expr b=expr) { r = a - b; }
> 
> | #(MULT a=expr b=expr) { r = a * b; }
> 
> | #(DIV a=expr b=expr) { r = a / b; }
> 
> | i:INT {r = (
> *int*)Integer.parseInt(i.getText());} 
> 
> ;
> 
> bexpr 
> *returns* [*boolean* r=*false*] { *int* a,b; } 
> 
> : #(EQUALS a=expr b=expr) {r = (a == b);}
> 
> | #(NOT_EQUALS a=expr b=expr) {r = (a != b);} 
> 
> | #(GT a=expr b=expr) {r = (a > b);}
> 
> | #(GTE a=expr b=expr) {r = (a >= b);}
> 
> | #(LT a=expr b=expr) {r = (a < b);}
> 
> | #(LTE a=expr b=expr) {r = (a <= b);}
> 
> ;
> 
> //logicalAndExpression returns [boolean r=false] { boolean a,b; }
> 
> // : #(AND a=bexpr b=bexpr) {r = (a && b); }
> 
> // ;
> 
> //logicalOrExpression returns [boolean r=false] {boolean a,b; }
> 
> // : #(OR a=logicalAndExpression b=logicalAndExpression) {r = (a || b);}
> 
> // ;
> 



-- 
Tarun Khanna
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