On November 10, 2021 12:19 PM, Jouke Witteveen wrote: > To: psm...@gnu.org > Cc: bug-make <bug-make@gnu.org> > Subject: Re: [PATCH 3/3] Introduce $(compare ...) for numerical comparison > > On Mon, Nov 8, 2021 at 4:08 PM Paul Smith <psm...@gnu.org> wrote: > > > > On Fri, 2021-07-16 at 14:04 +0200, Jouke Witteveen wrote: > > > +@item $(compare > > > +@var{lhs},@var{rhs},@var{lt-part}[,@var{eq-part}[,@var{gt-part}]]) > > > > Let me ask this: would it be better to use a format of: > > > > $(compare <lhs>, <rhs>, <eq>[, <lt>[, <gt>]]) > > > > Then the rule is, if the values are equal we get the <eq> part, if lhs > > is less than rhs we get <lt>, and if lhs is greater than rhs we get > > <gt>. > > > > If <gt> is not present then the invocation devolves to: > > > > $(compare <lhs>, <rhs>, <eq>, <!eq>) > > > > that is, the fourth arg is used for not equal. > > > > If <lt> is also not present then <eq> is used if the value is equal > > else it expands to the empty string. > > > > Cool, an alternative design that has something to go for it! Here is why I > like > the original design better. > > The only real difference is in four-argument usage. This alternative trades > the > 'ordered' nature of the arguments for favoring equality testing. To some > degree, equality testing is already possible through string-based equality > testing, and even if you really want to do a numerical equality check, the > original design allows you to do > > $(if $(compare <lhs>,<rhs>,,they_are_equal,),<eq>,<!eq>) > > In fact, in the original design you could get away with just the three- > argument version of $(compare) in combination with $(if), $(and) and $(or). > This is not the case for the alternative design. > > I also took a look at other languages. Nearly everywhere I could find three- > way comparisons, the possible outcomes are listed as LT, EQ, GT, in that > order. Fortran apparently had an "Arithmetic IF", that was also ordered as in > the original design of $(compare).
I have a similar function in my own fork called $(vcompare), which is similar, but does comparison of version-like strings. It does not have the additional arguments, which I would think are better separated off into a control function like $(if) instead of having then and else built into the $(compare). Randall