nix/tests/lang/eval-fail-foldlStrict-strict-op-application.nix
sternenseemann d0f2da214b primops: make nature of foldl' strictness clearer
* Clarify the documentation of foldl': That the arguments are forced
  before application (?) of `op` is necessarily true. What is important
  to stress is that we force every application of `op`, even when the
  value turns out to be unused.

* Move the example before the comment about strictness to make it less
  confusing: It is a general example and doesn't really showcase anything
  about foldl' strictness.

* Add test cases which nail down aspects of foldl' strictness:
  * The initial accumulator value is not forced unconditionally.
  * Applications of op are forced.
  * The list elements are not forced unconditionally.
2022-10-16 14:29:12 +02:00

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Nix

# Tests that the result of applying op is forced even if the value is never used
builtins.foldl'
(_: f: f null)
null
[ (_: throw "Not the final value, but is still forced!") (_: 23) ]