Re: Interactive parsing with Bison

[Hans Aberg]

On 28 Jun 2006, at 20:52, Richard Stallman wrote:

> > If the GUI outputs a Bison parser, you can then build it under the
> > control of make.  You could think of this kind of interface as an
> > alternate editor for .y files.
>
>     The kind of GUI that Satya (and I) are thinking of, is the one  
> that
>     one drops in some source files into the GUI, and it does the rest,
>     computing the dependicies.
>
> I do not understand what "dependencies" refers to in the context of
> Bison.  Are we talking about the same thing?

Oh, sorry, it should have been "file dependencies", i.e., how the  
file modification dates relate among files calling each other. When  
using 'make', these file dependencies are written down explicitly by  
giving the filesystem location of the files in the 'make' file, and  
'make' then checks the file modification dates, and if a dependent  
file has been modified, the associated action (like a compile) is  
initiated.

Now, the IDE's typically allows one to not having to write down these  
file dependencies explicitly, but merely indicating the source file.  
The IDE will then scan the source file for constructs such as  
'#include <filename>", identifying the file with file name  
'filename', adding it to the list of file dependencies of the source  
file, and also doing this recursively in the included file. This way,  
one only has to drop the source file into the IDE, and the IDE takes  
care of computing the files it is dependent on, and then also making  
sure the right compiles are taking place. This is very useful, but  
should not be viewed as a replacement of the explicit 'make' style,  
as the latter gives more control.

But 'make' could easily be extended to include such a feature: One  
needs a way to indicate that the source files should be scanned for  
file dependencies, the syntax for finding those files, whether the  
found files should be rescanned, etc.

In the case of a program like Bison, which produces files which  
should be compiled, such an IDE may have a way to indicate that some  
types files should be compiled before the others. After the compile,  
file dependancies must be recomputed. But I think 'make' already' has  
this capacity.

  Hans Aberg