Why is Failing Forward so disliked on these boards? [!silva]

Chamomile · Post by **Chamomile** » Wed Dec 24, 2014 7:53 am

~ also means "similar to" though. And while it's true that ~thing is not =thing and therefore literally qualifies as !thing, it carries a different connotation.

Ghremdal · Post by **Ghremdal** » Wed Dec 24, 2014 10:20 am

Leaving out the interesting symbol discussion, are there any systems that do failing forward well? By well I mean with clear guidelines and mechanics?

momothefiddler · Post by **momothefiddler** » Wed Dec 24, 2014 3:16 pm

Chamomile wrote:~ also means "similar to" though. And while it's true that ~thing is not =thing and therefore literally qualifies as !thing, it carries a different connotation.

Yep. Thus the tendency to use ¬ in formal situations, ~ (which looks similar (heh)) in informal keyboard situations, and ! in contexts where it's an explicit part of the syntax (e.g. C and its descendants). Or something.

also

http://en.wikipedia.org/wiki/List_of_ma ... al_symbols
"The symbol ! is primarily from computer science. It is avoided in mathematical texts, where the notation ¬A is preferred."
"The symbol ~ has many other uses, so ¬ or the slash notation is preferred. Computer scientists will often use ! but this is avoided in mathematical texts."

Blicero · Post by **Blicero** » Wed Dec 24, 2014 7:32 pm

I had one professor who would write things like "[backwards E] ! X" to mean "there exists a unique X". That does not appear to be a standard notation, though, at least according to that wikipedia article.

jadagul · Post by **jadagul** » Wed Dec 24, 2014 8:22 pm

Blicero wrote:I had one professor who would write things like "[backwards E] ! X" to mean "there exists a unique X". That does not appear to be a standard notation, though, at least according to that wikipedia article.

That's totally standard notation. "∃x" means "there exists an x", and "∃!x" means "there exists a unique x." It's pretty common in math classes, especially on blackboards (as opposed to textbooks, which can just write it out). It's also the standard "existential quantifier" in formal logic.

In fact, it's on the wikipedia page; search for "existential quantification" or "uniqueness quantification."

John Magnum · Post by **John Magnum** » Wed Dec 24, 2014 8:26 pm

Concurring with jadagul, that's a really common convention.

norms29 · Post by **norms29** » Wed Dec 24, 2014 8:27 pm

my entire time earning my B.S. in Mathematics I have only seen ! used as a not symbol in the programming class I had to take.

and Blicero, I don't know what in the wiki article gave you the idea it wasn't standard notation for uniqueness quantifier, they don't even list any alternate notation. there not being any alternative would seem to meet the strictest possible definition of uniqueness

Blicero · Post by **Blicero** » Wed Dec 24, 2014 8:44 pm

In an attempt to make myself look slightly less inept, I should note that I am familiar with the symbol for "there exists". I am obviously incapable of reading, though.

Josh_Kablack · Post by **Josh_Kablack** » Wed Dec 24, 2014 8:44 pm

Well online you can always use alt 170 to get ¬ or just cut n' paste that same ¬ from wikipedia's logical symbols page.

That way you also don't run into confusion with factorials.

momothefiddler · Post by **momothefiddler** » Thu Dec 25, 2014 1:05 am

Josh_Kablack wrote:Well online you can always use alt 170 to get ¬ or just cut n' paste that same ¬ from wikipedia's logical symbols page.

That way you also don't run into confusion with factorials.

I recommend this approach unless you're talking to a compiler who'll freak out about that (in which case it's reasonable to use !)

EDIT: in contexts where it's clear, I also use ~, but that's because I'm a lazy bastard