lix/src/libexpr
Eelco Dolstra 0dbd4638e0 * Two primops: builtins.intersectAttrs and builtins.functionArgs.
intersectAttrs returns the (right-biased) intersection between two
  attribute sets, e.g. every attribute from the second set that also
  exists in the first.  functionArgs returns the set of attributes
  expected by a function.

  The main goal of these is to allow the elimination of most of
  all-packages.nix.  Most package instantiations in all-packages.nix
  have this form:

    foo = import ./foo.nix {
      inherit a b c;
    };

  With intersectAttrs and functionArgs, this can be written as:

    foo = callPackage (import ./foo.nix) { };

  where

   callPackage = f: args:
     f ((builtins.intersectAttrs (builtins.functionArgs f) pkgs) // args);

  I.e., foo.nix is called with all attributes from "pkgs" that it
  actually needs (e.g., pkgs.a, pkgs.b and pkgs.c).  (callPackage can
  do any other generic package-level stuff we might want, such as
  applying makeOverridable.)  Of course, the automatically supplied
  arguments can be overriden if needed, e.g.

    foo = callPackage (import ./foo.nix) {
      c = c_version_2;
    };

  but for the vast majority of packages, this won't be needed.

  The advantages are to reduce the amount of typing needed to add a
  dependency (from three sites to two), and to reduce the number of
  trivial commits to all-packages.nix.  For the former, there have
  been two previous attempts:

    - Use "args: with args;" in the package's function definition.
      This however obscures the actual expected arguments of a
      function, which is very bad.

    - Use "{ arg1, arg2, ... }:" in the package's function definition
      (i.e. use the ellipis "..." to allow arbitrary additional
      arguments), and then call the function with all of "pkgs" as an
      argument.  But this inhibits error detection if you call it with
      an misspelled (or obsolete) argument.
2009-09-15 13:01:46 +00:00
..
attr-path.cc * Cleanup. 2007-01-13 14:21:49 +00:00
attr-path.hh * Use a proper namespace. 2006-09-04 21:06:23 +00:00
common-opts.cc * Option --argstr for passing string arguments easily. (NIX-75) 2007-01-14 12:32:44 +00:00
common-opts.hh * Option --argstr for passing string arguments easily. (NIX-75) 2007-01-14 12:32:44 +00:00
eval.cc * Allow unsafe (unspecified) comparisons between attrsets unless 2009-05-12 11:06:24 +00:00
eval.hh * Allow unsafe (unspecified) comparisons between attrsets unless 2009-05-12 11:06:24 +00:00
expr-to-xml.cc * Added an experimental feature suggested by Andres: ellipses ("...") 2008-08-14 14:00:44 +00:00
expr-to-xml.hh * Big cleanup of the semantics of paths, strings, contexts, string 2006-10-16 15:55:34 +00:00
get-drvs.cc * Support integers and lists of strings in meta fields. This is 2009-06-30 15:53:39 +00:00
get-drvs.hh * Support integers and lists of strings in meta fields. This is 2009-06-30 15:53:39 +00:00
lexer.l * Added an experimental feature suggested by Andres: ellipses ("...") 2008-08-14 14:00:44 +00:00
Makefile.am 2009-03-06 11:01:45 +00:00
names.cc * Export the nix-env derivation name parsing and version comparison 2008-07-01 10:10:32 +00:00
names.hh * Export the nix-env derivation name parsing and version comparison 2008-07-01 10:10:32 +00:00
nix.sdf First attempt to update Nix SDF grammar to match the actual bison grammar 2008-06-04 14:36:46 +00:00
nixexpr-ast.def * Some syntactic sugar for attribute sets: allow {x.y.z = ...;} as a 2009-05-15 12:35:23 +00:00
nixexpr.cc * Some syntactic sugar for attribute sets: allow {x.y.z = ...;} as a 2009-05-15 12:35:23 +00:00
nixexpr.hh * Some syntactic sugar for attribute sets: allow {x.y.z = ...;} as a 2009-05-15 12:35:23 +00:00
parser.hh * Use a proper namespace. 2006-09-04 21:06:23 +00:00
parser.y * Change the scoping of "inherit (e) ..." in recs so that the 2009-05-15 13:46:13 +00:00
primops.cc * Two primops: builtins.intersectAttrs and builtins.functionArgs. 2009-09-15 13:01:46 +00:00