Eelco Dolstra c4ac2a164a * The recent change in nixpkgs of calling `stdenv.mkDerivation' ... instead of `derivation' triggered a huge slowdown in the Nix expression evaluator. Total execution time of `nix-env -qa' went up by a factor of 60 or so. This scalability problem was caused by expressions such as (x: y: ... x ...) a b where `a' is a large term (say, the one in `all-packages-generic.nix'). Then the first beta-reduction would produce (y: ... a ...) b by substituting `a' for `x'. The second beta-reduction would then substitute `b' for `y' into the body `... a ...', which is a large term due to `a', and thus causes a large traversal to be performed by substitute() in the second reduction. This is however entirely redundant, since `a' cannot contain free variables (since we never substitute below a weak head normal form). The solution is to wrap substituted terms into a `Closed' constructor, i.e., subst(subs, Var(x)) = Closed(e) iff subs[x] = e have substitution not descent into closed terms, subst(subs, Closed(x)) = Closed(x) and otherwise ignore them for evaluation, eval(Closed(x)) = eval(x). * Fix a typo that caused incorrect substitutions to be performed in simple lambdas, e.g., `(x: x: x) a' would reduce to `(x: a)'.		2004-03-30 15:05:35 +00:00
..
eval.cc	* The recent change in nixpkgs of calling `stdenv.mkDerivation'	2004-03-30 15:05:35 +00:00
eval.hh	* Use a map to lookup primops.	2004-02-04 16:03:29 +00:00
lexer.l	* Added plain lambdas, e.g., `let { id = x: x; const = x: y: x; }'.	2004-03-28 20:34:22 +00:00
Makefile.am	* Allow linking against an external Berkeley DB / ATerm library.	2004-02-16 16:37:16 +00:00
nixexpr.cc	* The recent change in nixpkgs of calling `stdenv.mkDerivation'	2004-03-30 15:05:35 +00:00
nixexpr.hh	* Use a map to lookup primops.	2004-02-04 16:03:29 +00:00
parser.cc	* Extended the `inherit' syntax to optionally select attributes from	2004-02-04 17:23:26 +00:00
parser.hh	* Use a map to lookup primops.	2004-02-04 16:03:29 +00:00
parser.y	* Added an operator `?' to test for attribute existence, e.g.,	2004-03-28 21:15:01 +00:00
primops.cc	* Added an operator `~' to select paths within a derivation. E.g.,	2004-03-28 20:58:28 +00:00
primops.hh	* Use a map to lookup primops.	2004-02-04 16:03:29 +00:00