lib/tests: add more tests for fold functions
Also the invocation of tests is documented.
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@ -1,3 +1,6 @@
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# to run these tests:
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# nix-instantiate --eval --strict nixpkgs/lib/tests.nix
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# if the resulting list is empty, all tests passed
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let inherit (builtins) add; in
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with import ./default.nix;
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@ -45,9 +48,33 @@ runTests {
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expected = ["b" "c"];
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};
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testFold = {
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expr = fold (builtins.add) 0 (range 0 100);
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expected = 5050;
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testFold =
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let
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f = op: fold: fold op 0 (range 0 100);
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# fold with associative operator
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assoc = f builtins.add;
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# fold with non-associative operator
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nonAssoc = f builtins.sub;
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in {
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expr = {
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assocRight = assoc foldr;
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# right fold with assoc operator is same as left fold
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assocRightIsLeft = assoc foldr == assoc foldl;
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nonAssocRight = nonAssoc foldr;
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nonAssocLeft = nonAssoc foldl;
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# with non-assoc operator the fold results are not the same
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nonAssocRightIsNotLeft = nonAssoc foldl != nonAssoc foldr;
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# fold is an alias for foldr
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foldIsRight = nonAssoc fold == nonAssoc foldr;
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};
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expected = {
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assocRight = 5050;
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assocRightIsLeft = true;
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nonAssocRight = 50;
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nonAssocLeft = (-5050);
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nonAssocRightIsNotLeft = true;
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foldIsRight = true;
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};
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};
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testTake = testAllTrue [
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