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digitalmars.D.learn - Function declaration

reply "Casper =?UTF-8?B?RsOmcmdlbWFuZCI=?= <shorttail hotmail.com> writes:
Where is the function declaration in the language specification? 
I'm trying to parse a simple "void main() {}" with Pegged, but I 
can't figure our which declarations contain the function 
declaration. I tried with Pegged's example D grammar, but it's 
unwilling to parse said program.
Dec 24 2013
parent reply "Casper =?UTF-8?B?RsOmcmdlbWFuZCI=?= <shorttail hotmail.com> writes:
Never mind, found it. I searched for parameters and found it in 
http://dlang.org/declaration.html#DeclaratorSuffix
Thanks. :3
Dec 24 2013
parent reply Philippe Sigaud <philippe.sigaud gmail.com> writes:
On Wednesday, December 25, 2013,  <&quot;Casper F=C3=A6rgemand\&quot; &
lt;shorttail hotmail.com&gt;&quot; puremagic.com> wrote:

 Never mind, found it. I searched for parameters and found it in


http://dlang.org/declaration.html#DeclaratorSuffix

 Thanks. :3


I had a lot of problems with function declarations when testing the example
D grammar.  If you find any mistake in the provided D grammar, could you
push it as an issue in Pegged?
Dec 24 2013
parent reply "Casper =?UTF-8?B?RsOmcmdlbWFuZCI=?= <shorttail hotmail.com> writes:
On Wednesday, 25 December 2013 at 08:34:27 UTC, Philippe Sigaud 
wrote:

 On Wednesday, December 25, 2013,  <&quot;Casper 
 Færgemand\&quot; &
 lt;shorttail hotmail.com&gt;&quot; puremagic.com> wrote:

 Never mind, found it. I searched for parameters and found it in


 http://dlang.org/declaration.html#DeclaratorSuffix

 Thanks. :3


 I had a lot of problems with function declarations when testing 
 the example
 D grammar.  If you find any mistake in the provided D grammar, 
 could you
 push it as an issue in Pegged?


Yes, certainly.
Dec 25 2013
parent reply "Casper =?UTF-8?B?RsOmcmdlbWFuZCI=?= <shorttail hotmail.com> writes:
 From http://dlang.org/declaration.html#Parameter

Parameter:
     InOutopt BasicType Declarator
     InOutopt BasicType Declarator ...
     InOutopt BasicType Declarator = DefaultInitializerExpression
     InOutopt Type
     InOutopt Type ...

How do I add a declarator to a parameter like "char * format"? I 
altered the language specification to add a "InOutopt Type 
Declarator", but is there another way? The specification overall 
is really good, but I've found a few missing things elsewhere, 
and I'm wondering if it really is missing or I'm missing the 
point. :P I can't see any way to add a parameter name to 
something of type Type.
Dec 25 2013
next sibling parent reply Philippe Sigaud <philippe.sigaud gmail.com> writes:
On Wed, Dec 25, 2013 at 4:57 PM,  <"Casper Færgemand\"
<shorttail hotmail.com>" puremagic.com> wrote:

 From http://dlang.org/declaration.html#Parameter

 Parameter:
     InOutopt BasicType Declarator
     InOutopt BasicType Declarator ...
     InOutopt BasicType Declarator = DefaultInitializerExpression
     InOutopt Type
     InOutopt Type ...

 How do I add a declarator to a parameter like "char * format"? I altered the
 language specification to add a "InOutopt Type Declarator", but is there
 another way? The specification overall is really good, but I've found a few
 missing things elsewhere, and I'm wondering if it really is missing or I'm
 missing the point. :P I can't see any way to add a parameter name to
 something of type Type.


I'll consider that as a D grammar question, and not a Pegged-specific
question, since Pegged just uses a copy of the D site grammar :-)

As to this specific question, my answer is halas: I don't know. I find
parts of the D grammar a bit complicated for my taste (with 200
different rules, it's the most complicated programming language
grammar I know of). I'll let some grammar specialist answers there
(there are a few around these parts). I know some people have a
cleaned-up, alternate grammar, but I can't remember the link.
Dec 25 2013
parent reply "Casper =?UTF-8?B?RsOmcmdlbWFuZCI=?= <shorttail hotmail.com> writes:
On Wednesday, 25 December 2013 at 21:23:23 UTC, Philippe Sigaud 
wrote:

 I'll consider that as a D grammar question, and not a 
 Pegged-specific
 question, since Pegged just uses a copy of the D site grammar 
 :-)


Thank you regardless. I'll be sure to submit some issues once 
we're a bit further down the road. Error handling is what has 
displeased me the most so far, with only a single test case ever 
displaying something useful. I'm not sure what the solution 
should be though, perhaps the matches that munched the most 
tokens before failing?
Also, it should be possible to detect non-munching cycles aka. 
left recursion without too much extra compile time. It's funny 
because it's fine on compile time, but instant death at runtime. 
I'll post some of that once we're further.


On Wednesday, 25 December 2013 at 22:28:06 UTC, Timon Gehr wrote:

 The following is a parse tree for char* format:
 snip


Oooh, I missed that. I didn't think it possible one would dissect 
it like that. In my mind it would make more sense to keep char 
and * together, since it's a type of its own. Interesting. And 
weird.



 I consider the grammar specification (as well as some details 
 of what is valid syntax) to be quite inelegant, unnecessarily 
 repetitive and inconvenient for parser generators, but I am not 
 sure if a clean-up would be welcome.


I'm not sure. I haven't imported too much yet, but the only thing 
I've had to work around was left recursion in some arithmetic 
expressions (add and mul I believe). It's complicated for sure, 
but the language specification has survived nearly intact. My 
only past experience is the toy language Tiger made for education 
and stories I've been told of "normal" language specifications 
being really awful. So some copy paste is nice for a change.

I'd still like a look at a "clean" grammar if anyone has one 
around.
Dec 25 2013
parent Philippe Sigaud <philippe.sigaud gmail.com> writes:
On Thu, Dec 26, 2013 at 1:16 AM,  <"Casper Færgemand\"
<shorttail hotmail.com>" puremagic.com> wrote:

 On Wednesday, 25 December 2013 at 21:23:23 UTC, Philippe Sigaud wrote:

 I'll consider that as a D grammar question, and not a Pegged-specific
 question, since Pegged just uses a copy of the D site grammar :-)


 Thank you regardless. I'll be sure to submit some issues once we're a bit
 further down the road. Error handling is what has displeased me the most so
 far, with only a single test case ever displaying something useful. I'm not
 sure what the solution should be though, perhaps the matches that munched
 the most tokens before failing?


Error reporting in parser generator is a bit more difficult than for
hand-made parsers.
And moving around the info necessary to make a good report already
slows the parser by a factor of two.

As for what it the best report, I thought Pegged already provided the
rule that went farther?


 Also, it should be possible to detect non-munching cycles aka. left
 recursion without too much extra compile time. It's funny because it's fine
 on compile time, but instant death at runtime. I'll post some of that once
 we're further.


Yeah. I have a branch somewhere where I have many introspection
algorithms implemented (left recursion, rule reachability, null-rule
detection...). My goal is then to run them on request and block the
compilation when something is wrong.

The code is many months old already, I did not have the time to merge
it completely.See:

https://github.com/PhilippeSigaud/Pegged/blob/master/pegged/dev/introspection.d

I'd have to test it anew, with a new DMD.


 On Wednesday, 25 December 2013 at 22:28:06 UTC, Timon Gehr wrote:A>

 The following is a parse tree for char* format:
 snip


 Oooh, I missed that. I didn't think it possible one would dissect it like
 that. In my mind it would make more sense to keep char and * together, since
 it's a type of its own. Interesting. And weird.


Yeah, it took me a long time to understand that (I now remember).
Maybe it's because D evolved from C/C++ and it inherited some strange
quirks. The resulting language is clean enough (char* is a type), but
the grammar is sometimes weird.
Dec 26 2013
prev sibling parent Timon Gehr <timon.gehr gmx.ch> writes:
On 12/25/2013 04:57 PM, "Casper Færgemand" <shorttail hotmail.com>" wrote:

  From http://dlang.org/declaration.html#Parameter

 Parameter:
      InOutopt BasicType Declarator
      InOutopt BasicType Declarator ...
      InOutopt BasicType Declarator = DefaultInitializerExpression
      InOutopt Type
      InOutopt Type ...

 How do I add a declarator to a parameter like "char * format"? I altered
 the language specification to add a "InOutopt Type Declarator", but is
 there another way? The specification overall is really good, but I've
 found a few missing things elsewhere, and I'm wondering if it really is
 missing or I'm missing the point. :P I can't see any way to add a
 parameter name to something of type Type.


The following is a parse tree for char* format:

           Parameter
          /    |    \
         /     |     \
        /      |      \
       /   BasicType   \
  InOut_opt    |        \
           BasicTypeX   Declarator
               |       /   |      \
             'char'   / Identifier \
                     /     |       DeclaratorSuffixes_opt
                    /   'format'
                   /
            BasicType2Opt
                 /
           BasicType2
               /
             '*'

I consider the grammar specification (as well as some details of what is 
valid syntax) to be quite inelegant, unnecessarily repetitive and 
inconvenient for parser generators, but I am not sure if a clean-up 
would be welcome.
Dec 25 2013