This surprised me a bit. I didn’t find it documented but historically I have been quite bad at reading the docs. ?- format("~w~n", [foo,bar]). foo true. The opposite (not enough arguments) throws an error.

With this patch we get 101 ?- format("~w~n", [foo,bar]). foo ERROR: Format error: too many arguments ERROR: In: ERROR: [10] format("~w~n",[foo,bar]) ERROR: [9] <user> 102 ?- Let us see whether that results in too many broken programs … Having a flag to suppress errors that will be in the sy…

GNU Prolog 1.4.5 and YAP 6.5.0 git behaves as SWI-Prolog for that query. But ECLiPSe 7.0#49 and SICStus Prolog 4.5.0 throw an error reporting the surplus bar argument. I considered in the past implementing a lint check for this case but it’s relatively heavy to parse and check the arguments at compi…

I would vote for format with wrong # of args should throw an error (either too few or too many). It’s a mistake I often make and I would rather see an error than incorrect output. (But what about this breaking existing code? I hear you ask, and I reply “It was wrong code, and it’s probably easily fi…

I’m happy to add an error. What is the error term produced by SICStus and ECLiPSe? I don’t really see the obvious ISO style error term …

ECLiPSe: Version 7.0 #49 (x86_64_macosx), Wed Sep 18 19:49 2019 [user 36]: format("~w~n", [foo,bar]). foo bad argument list in format(output, "", [bar]) Abort [user 37]: catch(format("~w~n", [foo,bar]), Error, true). foo bad argument list in format(output, "", [bar]) Error = abort Yes (0.00s cpu) …

Abort is a bit drastic. Interesting. Is this consistency_error(Something, SomethingElse, WhyItIsInconsistent)?

My understanding is that, in ECLiPSe, most non-ISO errors throw an abort exception term. Joachim should be able to explain it better :stuck_out_tongue: You interpretation of the SICStus exception term is correct: https://sicstus.sics.se/sicstus/docs/latest4/html/sicstus.html/ref_002dere_002derr_002…

Currently, I see: $ swipl Welcome to SWI-Prolog (threaded, 64 bits, version 8.1.20-3-g369b0fa2a) SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software. Please run ?- license. for legal details. For online help and background, visit https://www.swi-prolog.org For built-in help, use ?-…

Good question. Opinions? I guess we have two options: format('too many arguments') consistency_error(format(X, Y), X, Y, format_arguments) and use this also for all the other format errors. Format/2,3 has quite a few currently fairly informative error messages. We map all of these to consist…

For the record, I have no strong opinion either way, as long as it is consistent. The lazy programmer in me tells me “whatever is the least work”.

too many arguments fits with the current too few arguments. consistency_error feels like “I know more about the error but I won’t tell you.” (And, yes, abort is too harsh.)

Too many arguments to format/2

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Too many arguments to format/2

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