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* Added syntactic sugar to the construction of attribute sets to

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`inherit' variables from the surrounding lexical scope.

  E.g.,

    {stdenv, libfoo}: derivation {
      builder = ./bla;
      inherit stdenv libfoo;
      xyzzy = 1;
    }

  is equivalent to

    {stdenv, libfoo}: derivation {
      builder = ./bla;
      stdenv = stdenv;
      libfoo = libfoo;
      xyzzy = 1;
    }

  Note that for mutually recursive attribute set definitions (`rec
  {...}'), this also works, that is, `rec {inherit x;}' is equivalent
  to `let {fresh = x; body = rec {x = fresh;};}', *not*
  `rec {x = x}'.
This commit is contained in:
Eelco Dolstra 2004-02-02 21:39:33 +00:00
parent d9f30fe7c7
commit 1c9c0a5a46
6 changed files with 78 additions and 41 deletions
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10
src/libexpr/nixexpr.cc
View file

@ -181,16 +181,18 @@ Expr substitute(const ATermMap & subs, Expr e)
}
/* Idem for a mutually recursive attribute set. */
ATermList bindings;
if (atMatch(m, e) >> "Rec" >> bindings) {
ATermList rbnds, nrbnds;
if (atMatch(m, e) >> "Rec" >> rbnds >> nrbnds) {
ATermMap subs2(subs);
for (ATermIterator i(bindings); i; ++i) {
for (ATermIterator i(rbnds); i; ++i) {
Expr e;
if (!(atMatch(m, *i) >> "Bind" >> s >> e))
abort(); /* can't happen */
subs2.remove(s);
}
return ATmake("Rec(<term>)", substitute(subs2, (ATerm) bindings));
return ATmake("Rec(<term>, <term>)",
substitute(subs2, (ATerm) rbnds),
substitute(subs, (ATerm) nrbnds));
}
if (ATgetType(e) == AT_APPL) {