Devs,
Shayan is working away on "Trees that grow"... do keep it on your radar:
To: ghc-devs
Sent: 25 May 2017 23:49
Do take a look at this:
* We propose to re-engineer HsSyn itself. This will touch a lot of
code.
* But it's very neat, and will bring big long-term advantages
Before all this, we may need to discuss a bit about the intended semantics
of
`Outputable`: does it need to print `PostRn`, or `PostTc` fields; or `Out`
suffixed constructors? If not, then we only need to write a set of
instances
for the base growable AST, once and for all. Such instances will be
I have been under the impression that we don't even want to print those.
On the contrary, inside GHC I /do/ want to print them. Otherwise how can I see
what the renamer has done?
Simon
From: Shayan Najd [mailto:sh.n...@gmail.com]
Sent: 28 July 2017 12:20
To: Simon Peyton Jones
Cc: ghc-devs@hask
>
> On the contrary, inside GHC I /do/ want to print them. Otherwise how can I
> see what the renamer has done?
Right. So if I understand correctly, with this semantics, `Outputable` is
somewhere between pretty printing as often used in program manipulation
libraries (like Haskell-Src-Exts (HSE))
by
(parser . prettyPrint . parser) = id
I meant
(prettyPrint . parser . prettyPrint) = id
for a valid input.
On Fri, Jul 28, 2017 at 4:32 PM, Shayan Najd wrote:
> On the contrary, inside GHC I /do/ want to print them. Otherwise how can I
>> see what the renamer has done?
>
>
> Right. So
Well, in GHC as it stands now (from 8.2.1), the original formulation is
correct.
The current pretty printer does not reproduce layout, but reparsing a
pretty printed ParsedSource will faithfully reproduce the original
ParsedSource (except for the Locations).
This is useful for constructing hsSyn
by
(parser . prettyPrint . parser) = id
I meant
(prettyPrint . parser . prettyPrint) = id
for a valid input.
Simplifying, (parser ∷ String → something), and (prettyPrint ∷ something
→ String).
Therefore, (parser . prettyPrint . parser ∷ String → something) and
(prettyPrint . parser
I agree. 4 is the current GHC invariant.
i.e., re-parsing a pretty printed parse tree gives you back a parse tree
identical to the original (ignoring SrcSpans)
Alan
On 28 July 2017 at 20:34, MarLinn wrote:
> by
>
> (parser . prettyPrint . parser) = id
>
> I meant
>
> (prettyPrint . parser . p
MarLinn,
Thanks for correcting me, and spelling this out.
I did mean what Alan mentioned: "re-parsing a pretty printed parse tree
gives you back a parse tree identical to the original (ignoring SrcSpans)".
As I recall, we had to go a bit further to give 'Something' some more
structure to t
I'm trying to port some plugin code from GHC 8.0.2 to GHC 8.2.1; alas I'm
getting an error suggesting that TyCon is no longer an instance of Ord:
Data/SBV/Plugin/Analyze.hs:580:33: error:
• No instance for (Ord TyCon) arising from a use of ‘M.lookup’
There are instances for similar types
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