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Re: [Help-gsl] gsl ode solver - const a problem?


From: Brian Gough
Subject: Re: [Help-gsl] gsl ode solver - const a problem?
Date: Mon, 21 Sep 2009 09:19:00 +0100
User-agent: Wanderlust/2.14.0 (Africa) Emacs/22.2 Mule/5.0 (SAKAKI)

At Fri, 18 Sep 2009 12:19:23 +0530,
Sumesh P.T. wrote:
> y is a const. I am facing an issue because of this.
> In my calculations, I pass a structure through params; but it so happens
> that y is also a member of the same structure 'params'
> In order to be using the correct modified values of y for all calculations I
> specify,
> params->... = &y[i]
> Now this gives me a warning during compilation as  "warning: assignment
> discards qualifiers from pointer target type" though it does the correction
> calculation. Obviously it is due to the 'const' in the definition of
> variable in the function func. Can some kind of typecasting help? will that
> be safe?

In general, it's a good idea to follow the C constness-rules.  If there
is a warning about const being discarded, it is usually a sign that
there is a better way to write that part of the code.  

It's not clear from your message what you need to do with y[i] but for
example, you could make a copy of any y[] values, instead of using a
pointer.  Note that you can also declare a "pointer to const" in a
struct, even if the struct is non-const, which would also avoid the
problem.

-- 
Brian Gough

GNU Scientific Library -
http://www.gnu.org/software/gsl/






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