[R] inconsistency in tryCatch...

[Richard O'Keefe]

I think the confusion is simple.
What you *really* wanted to do was
    tryCatch(print("fred"), -- other stuff --)
because the first argument of tryCatch is an EXPRESSION.  You don't need to
have 'function' in there anywhere at all.   Every function in R gets to
decide for itself which, if any, of its arguments are evaluated, and when.
NONE of the arguments of tryCatch is evaluated until tryCatch decides it is
time.  In most other programming languages, arguments are evaluated before
the call, and if you want something delayed, you have to wrap it in an
anonymous function.  Not R.d

So tryCatch
 - first sets up condition handling
 - THEN evaluates its first argument

On Thu, 23 Jun 2022 at 07:42, akshay kulkarni <akshay_e4 using hotmail.com> wrote:

> Dear Jeff,
>                Thanks! I think it is an idiosyncrasy of tryCatch? The
> other arguments like "error" doesn't need to be assigned to a call right?
> Just the definition would be sufficient, i think?
>
> Yours sincerely,
> AKSHAY M KULKARNI
> ________________________________
> From: Jeff Newmiller <jdnewmil using dcn.davis.ca.us>
> Sent: Thursday, June 23, 2022 12:53 AM
> To: r-help using r-project.org <r-help using r-project.org>; akshay kulkarni <
> akshay_e4 using hotmail.com>; R help Mailing list <r-help using r-project.org>
> Subject: Re: [R] inconsistency in tryCatch...
>
> You defined a function. You did not call the function. tryCatch returned
> the object you defined. So the interactive console printed the object
> returned.
>
> Invoking the "function" function does not call the defined function for
> you. Try:
>
> tryCatch((function() print("fred"))(), error = function(e) sum(1:3),
> finally = sum(1:3))
>
> On June 22, 2022 12:00:38 PM PDT, akshay kulkarni <akshay_e4 using hotmail.com>
> wrote:
> >Dear members,
> >                          I have the following code:
> >
> >        > tryCatch(function() print("fred"),  error = function(e)
> sum(1:3), finally = sum(1:3))
> >         function() print("fred")
> >
> >The expected output from the tryCatch call should be to print "fred" to
> the console, and exit, but as seen above, it is outputting
> >          function() print("fred")
> >
> >Can you people please shed some light on what is happening?
> >
> >thanking you,
> >Yours sincerely,
> >AKSHAY M KULKARNI
> >
> >       [[alternative HTML version deleted]]
> >
> >______________________________________________
> >R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
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> >PLEASE do read the posting guide
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> >and provide commented, minimal, self-contained, reproducible code.
>
> --
> Sent from my phone. Please excuse my brevity.
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
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> and provide commented, minimal, self-contained, reproducible code.
>

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