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Merge pull request #7158 from sternenseemann/foldl-strict-accumulation-value

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Valentin Gagarin 2023-02-19 23:54:14 +01:00 • committed by GitHub
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6 changed files with 25 additions and 3 deletions
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5
tests/lang/eval-fail-foldlStrict-strict-op-application.nix Normal file
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# 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) ]

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tests/lang/eval-okay-foldlStrict-lazy-elements.exp Normal file
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42

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tests/lang/eval-okay-foldlStrict-lazy-elements.nix Normal file
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# 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

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tests/lang/eval-okay-foldlStrict-lazy-initial-accumulator.exp Normal file
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42

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tests/lang/eval-okay-foldlStrict-lazy-initial-accumulator.nix Normal file
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# 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 ]