[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: dlang: initial changes to run the calc tests on it

From: Akim Demaille
Subject: Re: dlang: initial changes to run the calc tests on it
Date: Thu, 28 Feb 2019 22:19:02 +0100

Hi HS!

> Le 28 févr. 2019 à 07:32, H. S. Teoh <address@hidden> a écrit :
> On Tue, Feb 26, 2019 at 06:33:55PM +0100, Akim Demaille wrote:
> [...]
>> What I did below is quite ugly.  In particular, I don't know how to
>> write a decent scanner in D.  What I did is truly scary, a way to
>> force C code (with gets and ungetc) into my zero knowledge of D.  What
>> is the right way to do the following?
> [...]
> ungetc is a truly nasty hack of an API in C; is it really necessary to
> support that?

Certainly not!  I'm merely trying to get a scanner to feed our
parsers with tokens, and mimicking the C API is all my knowledge
of D allows me to do...

> D supports a range API that lets you query the front of a
> range (in this case, a stream of chars) without moving the current
> position of the stream. So ungetc really shouldn't be necessary unless
> it's an inextricable part of the Bison-generated parser.

It has nothing to do with Bison.  Bison generates parsers that pull
tokens from the scanner.  Tokens can be chars, but it should be
avoided IMHO: tokens are, well, tokens (terminal symbols coded as
ints for efficiency).

getc, ungetc are just one (common) way to write *scanners* in C.
And I need a simple scanner for our example, and our test suite.

> What I'd do is to templatize CalcLexer on an arbitrary input range of
> chars, and leave the specifics of binding to a File (or whatever else,
> like a string in a unittest) to the caller. And I wouldn't bother with
> using class inheritance at all, since I can't envision we'd ever need to
> swap in multiple lexers to the same parser.  So something like this:

This is already quite advanced compared to the current state of the
D skeleton.  What I'm looking for is a simple scanner that works with
what we have.  For instance below I tried to import your suggestion
into examples/d/calc.y, but it does not work.  Could you help me
make it work?  Just put it in examples/d/ and run "make check".

  GEN      examples/d/calc.d
  GEN      examples/d/calc
/opt/local/include/phobos/std/algorithm/iteration.d(475): Error: 
`this.__lambda11` has no value
examples/d/calc.d(920): Error: CTFE failed because of previous errors in `map`
examples/d/calc.d(921):        called from here: 


Attachment: calc.y
Description: Binary data

reply via email to

[Prev in Thread] Current Thread [Next in Thread]