On Fri, Dec 16, 2016 at 9:55 AM, Robert Haas <robertmh...@gmail.com> wrote:
> On Mon, Dec 5, 2016 at 12:32 PM, Robert Haas <robertmh...@gmail.com> > wrote: > >> - possible incremental implemention steps on this path: > >> > >> (1) minimal condition and expression, compatible with > >> a possible future full-blown expression syntax > >> > >> \if :variable > >> \if not :variable -- maybe \if ! :variable > We don't presently have a unary boolean operator named "!" so adding this variant would create an inconsistency > So I think it would be reasonable for somebody to implement \if, > \elseif, \endif first, with the argument having to be, precisely, a > single variable and nothing else (not even a negator). Then a future > patch could allow an expression there instead of a variable. I don't > think that would be any harder to review than going all the way to #5 > in one shot, and actually it might be simpler. I worry about the case of disallowing negation in #1 and then not getting to #5 (in the same version) where the expression "not(var)" becomes possible. If the expected committed patch set includes #5 then this becomes a matter for reviewer convenience so never mind. But if its at all possible for #5 to be punted down the road incorporating the eventual "not var" and "not(var)" syntax into #1 as a kind of shim would seem desirable. David J.
