Re: [Haskell-cafe] Safe lens?

There's no dependency on TH here. I'm hoping to do the same thing as I have done with fclabels, which is to have a Trustworthy module that imports Control.Lens.TH, derive lenses, and then allow all users of that data type to Safely import only the Getter/Setter modules. So, I'm curious: * Could Control.Lens.Getter have a LANGUAGE dependency it doesn't need? * Is there something fundamental in the design of lens (compared to fclabels), that its getters require unsafe language features? * Maybe the Internal module should be marked Trustworthy? Thanks, Greg On Mon, Oct 29, 2012 at 10:14 AM, Petr P wrote:

Hi

I believe the reason is that it uses TemplateHaskell for automatic derivation of labels. And TemplateHaskell is of course unsafe, since it could convert your code into something entirely different.

Best regards, Petr Pudlak

2012/10/29 Greg Fitzgerald :

...

Why are getters from the 'lens' package unsafe? Is there a subset like Data.Label.Pure from 'fclabels' that can be imported safely?

$ cat a.hs {-# LANGUAGE Safe #-}

import Control.Lens.Getter

main = print 123

$ runghc a.hs

a.hs:3:1: Control.Lens.Getter: Can't be safely imported! The module itself isn't safe.

Thanks, Greg

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