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Commit Graph

Author	SHA1	Message	Date
Eelco Dolstra	8a10360c91	* Simplify @-patterns: only `{attrs}@name' or `name@{attrs}' are now allowed. So `name1@name2', `{attrs1}@{attrs2}' and so on are now no longer legal. This is no big loss because they were not useful anyway. This also changes the output of builtins.toXML for @-patterns slightly.	2010-03-25 12:19:41 +00:00
Eelco Dolstra	9279174dde	* Added an experimental feature suggested by Andres: ellipses ("...") in attribute set pattern matches. This allows defining a function that takes at least the listed attributes, while ignoring additional attributes. For instance, {stdenv, fetchurl, fuse, ...}: stdenv.mkDerivation { ... }; defines a function that requires an attribute set that contains the specified attributes but ignores others. The main advantage is that we can then write in all-packages.nix aefs = import ../bla/aefs pkgs; instead of aefs = import ../bla/aefs { inherit stdenv fetchurl fuse; }; This saves a lot of typing (not to mention not having to update all-packages.nix with purely mechanical changes). It saves as much typing as the "args: with args;" style, but has the advantage that the function arguments are properly declared (not implicit in what the body of the "with" uses).	2008-08-14 14:00:44 +00:00
Eelco Dolstra	1b962fc720	* @-patterns as in Haskell. For instance, in a function definition f = args @ {x, y, z}: ...; `args' refers to the argument as a whole, which is further pattern-matched against the attribute set pattern {x, y, z}.	2008-08-14 12:53:29 +00:00

Author

SHA1

Message

Date

Eelco Dolstra

8a10360c91

* Simplify @-patterns: only `{attrs}@name' or `name@{attrs}' are now

allowed.  So `name1@name2', `{attrs1}@{attrs2}' and so on are now no
  longer legal.  This is no big loss because they were not useful
  anyway.

  This also changes the output of builtins.toXML for @-patterns
  slightly.

2010-03-25 12:19:41 +00:00

Eelco Dolstra

9279174dde

* Added an experimental feature suggested by Andres: ellipses ("...")

in attribute set pattern matches.  This allows defining a function
  that takes *at least* the listed attributes, while ignoring
  additional attributes.  For instance,

    {stdenv, fetchurl, fuse, ...}:
    
    stdenv.mkDerivation {
      ...
    };
    
  defines a function that requires an attribute set that contains the 
  specified attributes but ignores others.  The main advantage is that
  we can then write in all-packages.nix

    aefs = import ../bla/aefs pkgs;

  instead of

    aefs = import ../bla/aefs {
      inherit stdenv fetchurl fuse;
    };

  This saves a lot of typing (not to mention not having to update
  all-packages.nix with purely mechanical changes).  It saves as much
  typing as the "args: with args;" style, but has the advantage that
  the function arguments are properly declared (not implicit in what
  the body of the "with" uses).

2008-08-14 14:00:44 +00:00

Eelco Dolstra

1b962fc720

* @-patterns as in Haskell. For instance, in a function definition

f = args @ {x, y, z}: ...;

  `args' refers to the argument as a whole, which is further
  pattern-matched against the attribute set pattern {x, y, z}.

2008-08-14 12:53:29 +00:00

3 Commits