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