🚀 go-pugleaf

In article <brady-180193171852@brady.cs.tcd.ie>, brady@cs.tcd.ie (Michael Brady) writes:
> The draft of ISO Prolog talks about error handling, and says that when an
> error is discovered, an implicit throw(error(Code,Stuff)) is done, which
> can be caught by a catch/3 call made previously. The contents of Code is
> supposed to be one of a small number of atoms, and the Stuff is
> 'implementation defined'.
> 
> My question is, is there any informal agreement on what should be in Stuff?
> My specific question is about what should happen when input predicates
> return with syntax errors. If the stream is a window, and the user can
> correct the error, there needs to be enough information around somewhere
> for the input predicate to be retried. There's a number of ways to do this,
> so I wonder has any attempt at standardisation been attempted.
> 
> ---------------------
> Mike Brady
> Computer Science Department, Trinity College Dublin, Ireland

The next version of the draft standard will have a lot more detail on
the form of terms to be thrown when errors occur in standard built-in
predicates.  This is based on the U.S. proposal which is in the Annexe B of
N92, if that is the version that you have, but with some changes.  So
you will be able to detect the fact that a syntax error (as opposed to
some other error) occurred, and you will be able to specify what to do
when that happens.  Another thing to look at is the syntax_errors option
to read_term, which lets you specify whether read should just keep reading,
or fail, or raise an exception.  


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