« Return to Thread: how to see operators precedence in GHCi

Re: Re: how to see operators precedence in GHCi

by Stefan O'Rear :: Rate this Message:

On Wed, Jul 25, 2007 at 10:55:56AM -0700, Stefan O'Rear wrote:

> On Wed, Jul 25, 2007 at 09:35:38PM +0400, Bulat Ziganshin wrote:
> > Hello Jon,
> >
> > Wednesday, July 25, 2007, 8:07:57 PM, you wrote:
> > >> Q: how to see operators precedence in GHCi?
> > >> In the definition of `it': it = showParen $ (2 + (3 * 4))
> >
> > > Hmm, OK, but not that much quicker than going
> > > Prelude> :info (*)
> >
> > it just my poor english :) i mean - "how to see how Haskell will
> > parse some expression?". it will be too slow to look up each
> > precedence and parse expression by hand :)
>
> Much easier:
>
> stefan@stefans:~$ ghci
> GHCi, version 6.7.20070712: http://www.haskell.org/ghc/ :? for help
> Loading package base ... linking ... done.
> Prelude> :set -ddump-parsed
> Prelude> 2 + 3 * 4
>
> ==================== Parser ====================
> Just (2 + 3) * 4
>
>
> 14
> Prelude>

Uhm... that didn't work :)

Not quite as nice:

stefan@stefans:~$ ghci -ddump-rn-trace
GHCi, version 6.7.20070712: http://www.haskell.org/ghc/ :? for help
Top level:
tcRnStmt let __cmCompileExpr = System.IO.stdout
let __cmCompileExpr = GHC.Handle.stdout
[(rw, GHC.Handle.stdout)]
Loading package base ... linking ... done.
Top level:
tcRnStmt let __cmCompileExpr = System.IO.stderr
let __cmCompileExpr = GHC.Handle.stderr
[(rjJ, GHC.Handle.stderr)]
Top level:
tcRnStmt let __cmCompileExpr = System.IO.stdin
let __cmCompileExpr = GHC.Handle.stdin
[(rq, GHC.Handle.stdin)]
Prelude> 2 + 3 * 4
Top level:
tcRnStmt (2 + 3) * 4
2 + (3 * 4)
[(rqz, +), (rqA, *)]
14
Prelude>

Stefan

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« Return to Thread: how to see operators precedence in GHCi