nix/tests/lang/eval-okay-foldlStrict-lazy-initial-accumulator.nix

# Checks that the nul value for the accumulator is not forced unconditionally.
# Some languages provide a foldl' that is strict in this argument, but Nix does not.
builtins.foldl'
  (_: x: x)
  (throw "This is never forced")
  [ "but the results of applying op are" 42 ]
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. 2022-10-15 23:32:55 +00:00			`# Checks that the nul value for the accumulator is not forced unconditionally.`
			`# Some languages provide a foldl' that is strict in this argument, but Nix does not.`
			`builtins.foldl'`
			`(_: x: x)`
			`(throw "This is never forced")`
			`[ "but the results of applying op are" 42 ]`