[Template-haskell] reifyDecl problem

Sean Seefried sseefried@cse.unsw.EDU.AU
Tue, 22 Jul 2003 14:19:54 +1000 (EST)

> But Section 8.1 of "Template Meta-programming for Haskell" says:
> "In a similar way, reifyDecl f, gives a data structure
> that represens the value declaration for f;..."
> and later "... useful to restrict the use of reifyDecl to type
> constructors, classes, or variables (e.g. functions) declared at the
> top level..."
>  From that I made a conclusion that it is possible to reify function
> declarations (the most interesting ability of TH to me comparing with
> C++, for instance). And I still hope :) that it is possible and the
> error message above is just due to mere bug.

This you definitely can't do and oh, how I wish you could.  The closest
you can get is to define a function as reified code and then splice it.

d_fun = [d| fun = <function body> |]

And then you include $(d_fun) in another file to splice it in. This way
you have the reified code "d_fun" and fun is also in scope. You can
then manually write a lookup table of strings map to reified function