[Nix-dev] Re: [Nix-commits] SVN commit: nix - 18536 - MarcWeber - nixpkgs/trunk/pkgs/lib

[Nicolas Pierron]

Hi,

On Sun, Nov 22, 2009 at 22:28, Marc Weber <marco-oweber at gmx.de> wrote:
> Modified: nixpkgs/trunk/pkgs/lib/debug.nix
> ===================================================================
> --- nixpkgs/trunk/pkgs/lib/debug.nix    2009-11-22 21:28:28 UTC (rev 18535)
> +++ nixpkgs/trunk/pkgs/lib/debug.nix    2009-11-22 21:28:36 UTC (rev 18536)
> @@ -61,4 +65,47 @@
>       then [ { inherit name; expected = test.expected; result = test.expr; } ]
>       else [] ) tests));
>
> +
> +
> +  # evaluate everything once so that errors will occur earlier
> +  # hacky: traverse attrs by adding a dummy
> +  # ignores functions (should this behavior change?) See strictf
> +  #
> +  # Note: This should be a primop! Something like seq of haskell would be nice to
> +  # have as well. It's used fore debugging only anyway

I agree, this should be a prim-op which returns the result of the
evaluate expression.  By the way I don't think this would be too
difficult to add because there is already a "strictEvalExpr" function
which does the job.
The best should be to ask the opinion of Eelco because he has already
made some test on that.

> +  strict = x :
> +    let
> +        traverse = x :
> +          if isString x then true
> +          else if isAttrs x then
> +            if x ? outPath then true
> +            else all id (mapAttrsFlatten (n: traverse) x)
> +          else if isList x then
> +            all id (map traverse x)
> +          else if isBool x then true
> +          else if isFunction x then true
> +          else if isInt x then true
> +          else if x == null then true
> +          else true; # a (store) path?
> +    in if (traverse x) then x else throw "else never reached";

I have another implementation of such function:

strict = x:
  let r = builtins.tryEval (builtins.toXML x); in
    assert r.success; x

I prefer this implementation because I don't like the strictness of
the isType functions.


-- 
Nicolas Pierron
http://www.linkedin.com/in/nicolasbpierron - http://nbp.name/
Albert Einstein - Never memorize what you can look up on books.