#1544: Derived Read instances for recursive datatypes with infix constructors
are
too inefficient
-------------------------------------+--------------------------------------
Reporter: [EMAIL PROTECTED] | Owner:
Type: bug | Status: new
Priority: normal | Milestone: 6.8
Component: Compiler | Version: 6.6.1
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Os: Unknown | Testcase:
Architecture: Unknown |
-------------------------------------+--------------------------------------
Old description:
> Consider this definition:
> {{{
> data Exp = C | Exp :+: Exp | Exp :-: Exp deriving ( Read, Show )
> }}}
> Now, try something like:
> {{{
> > read "((((((((((C))))))))))" :: T
> }}}
> Even this simple expression may take several seconds to parse. It gets
> worse if you keep adding parenthesis. And even worse if you add more
> infix constructors....
New description:
Consider this definition:
{{{
data Exp = C | Exp :+: Exp | Exp :-: Exp deriving ( Read, Show )
}}}
Now, try something like:
{{{
> read "((((((((((C))))))))))" :: Exp
}}}
Even this simple expression may take several seconds to parse. It gets
worse if you keep adding parenthesis. And even worse if you add more infix
constructors....
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/1544>
GHC <http://www.haskell.org/ghc/>
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