[Gretl-devel] Re: Problems with quit keyword

On Sat, 27 Feb 2021, Artur Tarassow wrote: > Just by chance I've found this (weird?) behavior of the quit keyword > when using the GUI: > > 1) The following script fails to run. > 2) I get the somehow misleading message: > "Unbalanced "loop"/"endloop" in script" > > <hansl> > loop i=1..4 > >    if $i < 3 >        print "Gretl is awesome." >    elif $i == 3 >        print "Let's quit now." >        quit >    endif > endloop > </hansl> > > Another issue: The following script: > 1) Prints the message > 2) stdout prints "Script done" > 3) The GUI shows prints the error: > "Unmatched "if" in script (fixed)" > > <hansl> > FOO = 1 > if FOO == 1 >    print "gretl is awesome" >    quit > endif > </hansl> True, "quit" had a few issues. The "unmatched if" message is understandable (since we never get to "endif") but clearly unwanted. That's now fixed.

Other than that, quit had a "hair-trigger" quality: if you used it in a loop or a function its effect was to abort compilation as soon as it was encountered. This sort-of made sense if you were defining a function or loop via the GUI console, or in interactive use of gretlcli, but that's a pretty uncommon use-mode. Yesterday I put in place what I regard as a fix for functions: you can't use "quit" in a function. And today I'm doing the same for loops: no use of "quit" there either.

It surely makes sense that you can't quit inside a function: your options for getting out are (a) returning something or (b) breaking with an error flagged (funcerr or errorif). And with a loop (in a main script), if you want to quit you should use "break" first, so the loop can be torn down coherently. (In C you can use exit() anywhere, and that can have surprising results, for example if some third-party library you're linked against decides to call exit() on an error condition: "Why the heck did my program stop?!" We don't want that kind of uncontrolled exit in hansl.)