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authorsterni <sternenseemann@systemli.org>2023-06-26T23·20+0200
committerclbot <clbot@tvl.fyi>2023-07-11T16·17+0000
commit8adc9c56f21d8418dc5f4b73a4327d04cd10ebd3 (patch)
tree2ca1804e337763b359e79d26878cb9238bdfa54c /tvix/eval/src/tests/tvix_tests/notyetpassing/eval-okay-non-identifier-pointer-inequality.exp
parent4ba624efae2d63057c2bd5be23841be5017bd457 (diff)
docs(tvix): document when pointer equality is preserved in C++ Nix r/6405
This explicitly documents behavior of C++ Nix that goes against the
intuition you'd gather from this document: that e.g. a simple select
from an attribute set causes a value to no longer be pointer equal to
its former self.

The point of documenting this is that we can show in a to be written
section on the use of pointer equality in nixpkgs that pointer equality
is only needed in a limited sense for evaluating it (C++ Nix's exterior
pointer equality). Tvix's pointer equality is far more powerful since
value identity preserving operations also preserve pointer equality,
generally speaking (this is because we implement interior pointer
equality in my made up terminology). This should eventually also be
documented.

Change-Id: I6ce7ef2d67b012f5ebc92f9e81bba33fb9dce7d0
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8856
Tested-by: BuildkiteCI
Autosubmit: sterni <sternenseemann@systemli.org>
Reviewed-by: tazjin <tazjin@tvl.su>
Diffstat (limited to 'tvix/eval/src/tests/tvix_tests/notyetpassing/eval-okay-non-identifier-pointer-inequality.exp')
-rw-r--r--tvix/eval/src/tests/tvix_tests/notyetpassing/eval-okay-non-identifier-pointer-inequality.exp1
1 files changed, 1 insertions, 0 deletions
diff --git a/tvix/eval/src/tests/tvix_tests/notyetpassing/eval-okay-non-identifier-pointer-inequality.exp b/tvix/eval/src/tests/tvix_tests/notyetpassing/eval-okay-non-identifier-pointer-inequality.exp
new file mode 100644
index 000000000000..69fd1d084749
--- /dev/null
+++ b/tvix/eval/src/tests/tvix_tests/notyetpassing/eval-okay-non-identifier-pointer-inequality.exp
@@ -0,0 +1 @@
+[ false false false false false true false false ]