[antlr-interest] need help designing a simple calculator

[Andrew Deren]

You can look at my calculator example/implenentation. I used antlr for that
application and have implementation in java and C#. I have a very simple
example (calculator with variables and functions) and then took that into
more of a language. I do not use the antlr tree building, but I'm building
my own custom made AST.
You can download it from http://www.adersoftware.com/?page=compilers
Andrew

----- Original Message -----
From: "fedot" <fedot at stockworm.com>
To: <antlr-interest at yahoogroups.com>
Sent: Monday, March 10, 2003 3:21 PM
Subject: [antlr-interest] need help designing a simple calculator


> Having read through just about all ANTLR documentation I could lay
> my hands on, I am sorry to say that I am more frustrated than
> enlightened at this point. I would be greatly thankful if anyone
> experienced enough with ANTLR could lend me a hand with the
> following task:
>
> I need to design a parser capable of evaluating one-liner boolean
> equations, such as:
>
>     "F1(A, 5) AND F2(B)"
>     "A <= 0.4 AND F1(B, 1) OR F2(C, 2)"
>     "NOT (A <> 10 AND B < 0.5)"
>
> Or more specifically, being able to perform the following operations
> (in order of precedence):
>
> OR
> AND
> = <>
> < <= > >=
> + -
> * /
> NOT
>
> Variables are given as a map of name/value pairs, and list of
> functions is fixed and known ahead of time.
>
> Attached is my first shot at lexer/parser to do the job. I am still
> not sure what direction I should take next, as I am not at all
> comfortable yet with ANTLR and not familiar with all of its
> capabilities. Specifically, I have the following questions to answer:
>
> 1) do I need to build an AST and use a TreeParser to actually
> evaluate my expressions? or do I just do it all within the parser?
>
> 2) i know why I am getting ambiguity warnings about conflicts
> between "AND/OR/NOT" operators and ID identifiers, but what should I
> do about eliminating that ambuguity?
>
> 3) i don't think i did the right thing with unary_expression being a
> NUMBER constant, a parenthesized "expression", an ID (variable), or
> a function call. or did i? it seems that ID and function should be
> two separate rules instead of one with optional function arguments.
>
> Like I said, you would be doing me a GREAT favor if you could point
> me in the right direction.
>
> Thank you!
>
> ---------------------------
>
> // Parser
> class SignalParser extends Parser;
>
> options {
>     buildAST = true;
> }
>
> expression:
>     logical_or_expression
> ;
>
> logical_or_expression:
>     logical_and_expression (OR^ logical_and_expression)*
> ;
>
> logical_and_expression:
>     equality_expression (AND^ equality_expression)*
> ;
>
> equality_expression:
>     relational_expression ((EQ^ | NE^) relational_expression)*
> ;
>
> relational_expression:
>     additive_expression ((LT^ | LE^ | GT^ | GE^) additive_expression)
> *
> ;
>
> additive_expression:
>     multiplicative_expression ((ADD^ | SUBTRACT^)
> multiplicative_expression)*
> ;
>
> multiplicative_expression:
>     unary_expression ((MULTIPLY^ | DIVIDE^) unary_expression)*
> ;
>
> unary_expression:
>     NUMBER
>     |
>     LPAREN! expression RPAREN!
>     |
>     ID (LPAREN! (expression (COMMA! expression)*)? RPAREN!)?
> ;
>
> // Lexer
> class SignalLexer extends Lexer;
>
> options {
>     k = 2;
> }
>
> WHITESPACE:
>     (' ' | '\t' | '\n' { newline(); } | '\r') { $setType
> (Token.SKIP); }
> ;
>
> NUMBER:
>     (DIGIT)+  ('.' (DIGIT)*)? (EXPONENT)? | '.' (DIGIT)+ (EXPONENT)?
> ;
>
> ID:
>     ('a'..'z' | 'A'..'Z' | '_') ('a'..'z' | 'A'..'Z' | '_'
> | '0'..'9')*
> ;
>
> protected
> DIGIT:
>     '0'..'9'
> ;
>
> protected
> EXPONENT:
>     ('e' | 'E') ('+' | '-')? (DIGIT)+
> ;
>
> LPAREN: "(" ;
> RPAREN: ")" ;
> COMMA: "," ;
>
> OR: "OR" ;
> AND: "AND" ;
>
> EQ: "=" ;
> NE: "<>" ;
>
> LT: "<" ;
> LE: "<=" ;
> GT: ">" ;
> GE: ">=" ;
>
> ADD: "+" ;
> SUBTRACT: "-" ;
>
> MULTIPLY: "*" ;
> DIVIDE: "/" ;
>
> NOT: "NOT" ;
>
>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
>



 

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