From: eregontp@... Date: 2018-02-15T12:10:07+00:00 Subject: [ruby-core:85584] [Ruby trunk Feature#14478] String #uminus should de-dupe unconditionally Issue #14478 has been updated by Eregon (Benoit Daloze). Since it's var = -str, it's very clear the return value should be used (and deduped) and we can't expect `str` to changed. So if the only concern is returning str if str is frozen in -str, I agree that seems a very low compatibility risk. ---------------------------------------- Feature #14478: String #uminus should de-dupe unconditionally https://bugs.ruby-lang.org/issues/14478#change-70380 * Author: sam.saffron (Sam Saffron) * Status: Open * Priority: Normal * Assignee: * Target version: ---------------------------------------- continuing: https://bugs.ruby-lang.org/issues/14475 Current documentation for String uminus says: "If the string is frozen, then return the string itself." Trouble is that there is no simple way to de-duplicate unconditionally without inefficiency: Say `x` is an arbitrary string (either frozen or unfrozen) : ``` x = -x # may return a non fstring x = -+x # will return fstring, but makes an unneeded copy x = -x.dup # fstring again, uneeded copy x = x.frozen? ? -+x : -x # too verbose, uneeded copy ``` Instead why not change it so `-` is deduped unconditionally? I would argue this is worth backporting, cause if we are making fstring optimisations now, we are going to be stuck with legacy inefficient code going forward. An alternative may be a c-extension gem that adds #fstring to String but that just feel wrong. I think the documentation should say: String uminus says: "If the string is de-duplicated, then return the string itself." Happy to make the change it is quite simple:`(FL_TEST(str, RSTRING_FSTR)` -- https://bugs.ruby-lang.org/ Unsubscribe: