Tenaja,
The option of which you are thinking is "target", not "output". The
target option specifies the language for which you would like the parser
to be generated; the output option specifies the type of information
produced by a call to one of the functions in the generated code.
I am not familiar with any five minute intro that would give you the
information you want other than the ANTLR book I mentioned in the
previous e-mail. The following might help, but please bear in mind that
this is all off of the top of my head. :)
So consider the grammar
grammar Simple;
options { target=Java; }
program: decl*;
decl: IDENTIFIER '{' statement* '}';
statement: '+' | '-';
IDENTIFIER: ('a'..'z')*;
WS: ('\n' | '\r' | '\t' | ' ')* { skip(); } ;
This grammar would recognize any of the following code:
foo { + - - + }
bar { - + }
stuff { + + + }
but it wouldn't produce any output; that is, the SimpleParser.program()
method has a void return. If you want output, you have to specify it in
the grammar. Consider the following rewrite:
grammar Simple;
options { target=Java; output=AST; }
tokens { PROG; DECL; }
program: decl* -> ^(PROG decl*);
decl: IDENTIFIER '{' statement* '}' -> ^(DECL statement*);
statement: '+' | '-';
IDENTIFIER: ('a'..'z')*;
WS: ('\n' | '\r' | '\t' | ' ')* { skip(); } ;
Now, the SimpleParser.program() method will have a return value of a
type generated by ANTLR. That type will have a public member named
"tree". By default, tree has type Object but actually contains a
CommonTree; that CommonTree is a homogenously-typed AST which contains
the parse of the input. There are also instructions on the ANTLR site
for causing the grammar to produce heterogeneously-typed ASTs.
In the project on which I am working, we have to create nodes through a
factory. As a result, we went with an alternative approach: manually
controlling the output of the grammar rules. Our rules look something
like this:
fieldDeclaration returns [FieldDeclarationNode ret]
:
fieldModifiers
type
variableDeclarators
';'
{
$ret = factory.makeFieldDeclarationNode(
$fieldModifiers.ret, $type.ret,
$variableDeclarators.ret);
}
;
Does this answer your question about using the output of the ANTLR parser?
In terms of licensing, I would expect that the generated parser is not
covered by the BSD license unless the original grammar file is covered
by the BSD license. I have this impression for the same reason that the
exported PNG from a Microsoft Visio document isn't subject to any
licensing restrictions from the Visio software itself; it's merely
subject to restrictions which were on the original .vsd file. But I
could be wrong about this; you'd have to ask the more lawyer-y people on
the list to be sure.
Cheers,
Zach
> Zach,
> Thank you for responding. I think maybe my inquiry was unclear. I've read the
> "five minute intro..." and have used antlr to process several samples,
> producing code in Java, C, C#, etc,. (It's very simple...) Unless the
> output=AST is different from those output commands (output = csharp), it is
> probably not what I'm interested in.
>
> What I'm looking for is a 5-minute tutorial on using the output; for
> instance, sending a file to the compiled C# output, and having that C# code
> process the text file and generate a result. My end goal is a simple
> compiler to produce some Intermediate Representation (Three-Address, or
> PCode, etc).
>
> ...
> On another topic, regarding the BSD license, since this is the first time
> I've worked with o/s code generation tools.
> .....The non-C output does not include a copy of it.
> .....The C output includes the BSD notice at the top.
> So, does that mean that I'm free to compile and distribute binary forms of
> Java& C# output code without the license, but not C? Does that mean the only
> requirements for distributing the C in binary form are to put it in an About
> box, or something equivelant? Why would the C output require it, but not the
> other languages? I may eventually turn this into a commercial product so I'd
> like to know how much disclosure is required.
>
> Thanks!!!
>
> --- On Sun, 11/7/10, Zachary Palmer<[email protected]> wrote:
>
>
> From: Zachary Palmer<[email protected]>
> Subject: Re: [antlr-interest] Tutorial... actuala use?
> To: [email protected]
> Date: Sunday, November 7, 2010, 5:16 PM
>
>
> Tenaja,
>
> By default, the generated ANTLR grammar is just a recognizer: it will
> throw an exception in the presence of a string not in the grammar and it
> will terminate normally in the presence of a string in the grammar. To
> get more output from ANTLR (such as an AST), you probably want to set
> "output=..." in the options section of your grammar. For an informal
> discussion of "output=AST", try
> http://www.antlr.org/wiki/display/ANTLR3/Tree+construction . For more
> detailed information, there is a relatively inexpensive book ("The
> Definitive ANTLR Reference") that you can buy in electronic form.
>
> For more examples, you might try taking a glance at some of the grammars
> on the ANTLR site (http://www.antlr.org/grammar/list). There's also a
> somewhat non-standard approach that I've been forced to use (due to some
> strange constraints in my project) which is illustrated by the ANTLR
> grammar used in a branch of the OpenJDK project in which each rule
> explicitly returns the values that it needs (which are then set by
> grammar actions).
>
> Cheers,
>
> Zach
>
>> I'm familiar with bnf (etc) files, and have written a simple r/d compiler
>> myself. I'm looking at antlr for expanding, and for maintenance reason. As
>> such, I'd like to put together one of my simple bnf languages and view the
>> output. I've seen a few antlr tutorials, but haven't found one that really
>> describes the compiled code output (not the antlr output, but what a
>> compiled exe or java file output produces).
>>
>> So... can someone point me to a tutorial that shows what to do AFTER you
>> compile the anltr-generated file?
>>
>> Thanks!
>> Tenaja
>>
>>
>>
>>
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