Re: how to parse linear equations

[Hans Aberg]

[Please keep the cc to the Help-Bison list, so that others can help.]

On 16 Jan 2010, at 19:00, Michael Chen wrote:

> If I use an array to hold the coefficients. Do I dynamically allocate
> an array ...

If, at least for a start until you know the other things work, you use  
an array that can hold all the information and restrict to a fixed  
maximum number of equations, you do not need to dynamically allocate.

Otherwise, a polymorphic pointer is convenient. I use C++ which has  
language support for it via virtual class functions, and cleanup via  
destructors.

Others here use C, and can explain; typically a pointer void*, using  
Bison's type system sorting it out. Then one has to do the cleanup by  
hand in the actions, plus writing some special code (it was %error or  
something) for handling parse error recovery (if you do that), as the  
rule actions are not executed at this time.

> ...for each leaf node of the ast tree?

One can use a reference count in order to avoid always creating a new  
object. If the actions typically build new objects, this may not have  
much impact on the execution time of the code.

You might also not worry about memory leaks for a start, fixing that  
later when you have some working code.

  Hans