Another way to think of it could be to interpret the operator as asking, "do the arguments supplied form an equivalence class <https://en.wikipedia.org/wiki/Equivalence_class>?" If only one argument is supplied, then it trivially forms such a class.
On Sun, Nov 24, 2019 at 10:27 PM George Neuner <gneun...@comcast.net> wrote: > > > On 11/24/2019 5:30 PM, Jonathan Simpson wrote: > > The documentation for char=? leaves the impression that it takes a minimum > of two arguments: > > > https://docs.racket-lang.org/reference/characters.html?q=expand#%28def._%28%28quote._~23~25kernel%29._char~3d~3f%29%29 > > If a single character is passed as argument 1, char=? returns true. To me, > '=' implies at least two things to compare. The other functions in this > family appear to behave the same way. > > There is a note saying that since 7.0 the functions accept one argument. > Any reason for this change? At the very least I think the documentation > could make this clearer(probably because the docs were originally written > when it required two arguments). > > -- Jonathan > > > I don't know the developers' reasoning, but I can guess. > > Predicates already were variadic taking 2 or more arguments (at least > since R3RS, circa 1986), and they behave like a fold/reduce with an implied > base/identity value. I think the idea is that they should work with any > non-empty list of arguments. > > FWIW, Common Lisp's predicates always have behaved in this way. > > YMMV, > George > > -- > You received this message because you are subscribed to the Google Groups > "Racket Users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to racket-users+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/racket-users/224f2bfe-1ee5-7a49-855f-19c21e202a83%40comcast.net > <https://groups.google.com/d/msgid/racket-users/224f2bfe-1ee5-7a49-855f-19c21e202a83%40comcast.net?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CACQBWFmPb26SQVrHhgg%3Djdvyc8u3-j8pFt2KkzGek6eXW_mbMA%40mail.gmail.com.
