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Q32 syntax correction in instructions #39

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2 changes: 1 addition & 1 deletion questions.json
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Expand Up @@ -250,7 +250,7 @@
{
"topic": "Reimplementation: attrVals",
"path": "reimplementation/attrVals",
"question": " Write your own implementation of the `attrVals` function.\n\n It consumes a list of `attribute names` and an \n `attribute set`. It returnes the values of each \n `attribute name`.\n \n**Note**: Remember that `attrSet ? \"a\"` returns `true` and `attrSet ? \"j\"` => `false`!\n\n**Note**: Remember that `key = a; attrSet.${key}` returns `1`!\n\n###`attrVals` vs `attrValues`: \n\n* `attrVals` -> given a list of names, extract their values from the set and return a list of them\n\n `attrVals [\"a\" \"b\" \"c\"] attrSet; => should be [1 2 3]` \n\n* `attrValues` -> extract all values in the given set and return a list of them\n\n `attrValues attrSet; => [1 2 3 4]`\n\n**Warning:** This is hard!",
"question": " Write your own implementation of the `attrVals` function.\n\n It consumes a list of `attribute names` and an \n `attribute set`. It returnes the values of each \n `attribute name`.\n \n**Note**: Remember that `attrSet ? \"a\"` returns `true` and `attrSet ? \"j\"` => `false`!\n\n**Note**: Remember that `key = \"a\"; attrSet.${key}` returns `1`!\n\n###`attrVals` vs `attrValues`: \n\n* `attrVals` -> given a list of names, extract their values from the set and return a list of them\n\n `attrVals [\"a\" \"b\" \"c\"] attrSet; => should be [1 2 3]` \n\n* `attrValues` -> extract all values in the given set and return a list of them\n\n `attrValues attrSet; => [1 2 3 4]`\n\n**Warning:** This is hard!",
"code": "with import <nixpkgs> { };\nlet\n attrSet = {c = 3; a = 1; b = 2; d=4;};\n\n #tips: use the map function and access the attribute values \n attrVals = XXX;\n\nin\nrec {\n\n solution = attrVals [\"a\" \"b\" \"c\"] attrSet; #should be [1 2 3]\n}\n",
"solution": "\nwith import <nixpkgs> { };\nlet\n attrSet = {c = 3; a = 1; b = 2; d=4;};\n attrVals = kys: se: lib.fold (el: c: if se ? \"${el}\" then [(se.${el})] ++ c else c) [] kys;\n\nin\nrec {\n\n solution = attrVals [\"a\" \"b\" \"c\"] attrSet; #should be [1 2 3]\n}\n\n",
"youtube": "https://www.youtube.com/watch?v=CQAeAyRX1zs&list=PLMr2KA8WWojv-4cgqIiVebml0FrMl8N_-"
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