[Haskell-cafe] GHC Extension Proposal: ArgumentBlock

Manuel Gómez targen at gmail.com
Sun Sep 6 19:03:28 UTC 2015

On Sun, Sep 6, 2015 at 1:58 PM, Andrew Gibiansky
<andrew.gibiansky at gmail.com> wrote:
> A few more things to add to this discussion:
> 1. In terms of impact, I think it makes sense to view this extension as similar to -XDoAndIfThenElse and -XLambdaCase. Both are similar in their levels of complexity and add a similar amount of syntax. Would GHC be better off without them? Or do we expect that some future version of GHC may have one or both of them on by default? I think that if we ever want to change basic Haskell syntax (such as DoAndIfThenElse and ArgumentBlock), we have to start it off with an extension.
> 2. Following up on that, perhaps another way to view this question is: Do we ever want this functionality to be part of standard Haskell? If not, then I would vote against this extension, because it just adds fragmentation. If there's a possibility that we may want to permanently change default syntax a la ArgumentBlock, then we have to start off with an extension. (FYI I believe it is a valid possibility, in that the extension is inherently backwards compatible -- it should not break any code if it is enabled, as it allows strictly more parses.)

It seems to me that lately the community’s visible attitude has
shifted toward a heightened value of stability and uniformity for
Haskell and its software ecosystem, and experimentation, fragmentation
and diversity in styles and dialects are now viewed as threatening.
This drives us to reject the process of gradual improvement that has
made Haskell great over the years.  Other similarly purely syntactic
extensions seem to me to have been met with less resistance in the
past.  It appears we’re now far more concerned with the pursuit of


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