Re: [Help-glpk] [PATCH] determine whether we are handling an error

[Andrew Makhorin]

On Thu, 2015-11-05 at 22:57 +0100, Jeroen Demeyer wrote:
> On 2015-11-05 22:20, Heinrich Schuchardt wrote:
> > Hello Jeroen,
> >
> > could you, please, describe the use case for the patch.
> 
> My use case is really for using GLPK through SageMath, which is a 
> mathematical program with an interactive Python interface. I want to 
> convert GLPK errors to Python exceptions. For this I install an error 
> hook and a term hook. But I need to distinguish between normal messages 
> and error messages.

Thank you for your suggestion and the patch provided.

I will add the following API routine:

------------------------------------------------------------------------
NAME

glp_at_error - check for error state

SYNOPSIS

int glp_at_error(void);

DESCRIPTION

The routine glp_at_error checks if the GLPK environment is at error 
state, i.e. if the call to this routine is (indirectly) made from the
glp_error routine via an user-defined hook routine.

RETURNS

If the GLPK environment is at error state, the routine glp_at_error
returns non-zero, otherwise zero.
------------------------------------------------------------------------

> 
> > Currently both normal messages and error messages are sent to stdout,
> > which does not match usual usage of output streams.
> >
> > I propose to store the information if an error message is written in
> > env->term_out and to use a new value GLP_ERROR = 2 to indicate an error
> > message.
> >
> > This value then should be used in glp_puts to decide if a message shall
> > be sent to stdout or stderr.
> >
> > An API function could be provided to read env->term_out. The return
> > value could be used in the terminal hook function.
> 
> Sure, I don't really care so much *how* this feature is added. I 
> implemented it the way I did mainly because it was the simplest solution.
> 
> 
> Jeroen.
> 
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