nix/tests/functional/lang/eval-okay-foldlStrict-lazy-elements.nix

# Tests that the rhs argument of op is not forced unconditionally
let
  lst = builtins.foldl'
    (acc: x: acc ++ [ x ])
    [ ]
    [ 42 (throw "this shouldn't be evaluated") ];
in

builtins.head lst
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			`# Tests that the rhs argument of op is not forced unconditionally`
			`let`
			`lst = builtins.foldl'`
			`(acc: x: acc ++ [ x ])`
			`[ ]`
			`[ 42 (throw "this shouldn't be evaluated") ];`
			`in`

			`builtins.head lst`