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

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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).
This commit is contained in:
Eelco Dolstra 2008-08-14 14:00:44 +00:00
parent db4f4a8425
commit 9279174dde
14 changed files with 57 additions and 23 deletions
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5
src/libexpr/nixexpr.cc
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@ -114,12 +114,13 @@ static void varsBoundByPattern(ATermMap & map, Pattern pat)
{
ATerm name;
ATermList formals;
Pattern pat1, pat2;
Pattern pat1, pat2;
ATermBool ellipsis;
/* Use makeRemoved() so that it can be used directly in
substitute(). */
if (matchVarPat(pat, name))
map.set(name, makeRemoved());
else if (matchAttrsPat(pat, formals)) {
else if (matchAttrsPat(pat, formals, ellipsis)) {
for (ATermIterator i(formals); i; ++i) {
ATerm d1;
if (!matchFormal(*i, name, d1)) abort();