[Template-haskell] declaration splicing

[Lemmih]

On Mon, 14 Mar 2005 01:38:25 +0800 (GMT-8), WANG Meng
<wangmeng at comp.nus.edu.sg> wrote:
> 
> > >From http://www.haskell.org/ghc/docs/6.4/html/users_guide/template-haskell.html:
> > 'Note that the syntax for a declaration splice uses "$" not "splice"
> > as in the paper. Also the type of the enclosed expression must be Q
> > [Dec], not [Q Dec]  as in the paper.'
> 
> Thank you for your reply. I also tried to use "$". But GHC gives
> 
> *Main> $(myparseDec "x=1")
> 
> <interactive>:1:
>     Couldn't match `Exp' against `Dec'
>         Expected type: ExpQ
>         Inferred type: Q Dec
>     In the application `myparseDec "x=1"'
>     In the definition of `it': it = $[splice](myparseDec "x=1")
> 
> It seems "$" only takes in an "Q Exp".

You can't splice top level declarations from the interactive prompt.
Save the code in a file and all will be well. (Notice that the TH code
can't be in the module where the splicing takes place, and that your
function should have the type 'Q [Dec]' instead of 'Q Dec'.)

-- 
Friendly,
  Lemmih