Hi Henrik, On 9 July 2016 at 09:46, Henrik Nilsson <henrik.nils...@nottingham.ac.uk> wrote: > Hi all, > > On 07/09/2016 08:09 AM, C Maeder wrote: >> >> The asymmetry that you mention is already apparent for (Haskell98) infix >> expressions, i.e. when "composing" lambda- or if-expression: >> >> (if c then f else g) . \ x -> h x >> >> Parentheses around the last argument of "." do not matter, but >> parentheses around the first argument make a real difference > > > But that has to do with how grammatical ambiguity related to > in this case "if" and "lambda" are resolved by letting > the constructs extend as far as possible to the right. > > This the standard way of resolving that kind of ambiguity > across a very wide range of programming languages and parsing > tools (e.g. preferring shift over reduce in an LR parser). > (And also in principle how lexical ambiguities are typically > resolved, sometimes referred to as the "maximal munch rule".) > > In contrast, the present proposal suggests treating > different argument positions in grammatically > different ways (different non-terminals). As far as I know, > that is unprecedented. And in any case, it manifestly > complicates the grammar (more non-terminals) and as > a consequence adds another grammatical hurdle to > learning the language.
Thank you for pointing this out. I have updated the proposal so that it doesn't introduce a new non-terminal. I'm not sure if it should be implemented this way in the GHC parser, but this is probably a separate question. - Akio _______________________________________________ Glasgow-haskell-users mailing list Glasgow-haskell-users@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/glasgow-haskell-users
