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Clean up group-by descriptions & spelling

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This commit is contained in:
Colin Jones 2014-01-21 08:06:34 -06:00
parent d6b1b57942
commit 86a6790ae4
2 changed files with 15 additions and 12 deletions
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4
resources/koans.clj
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@ -216,7 +216,7 @@
{:last-name "Smith" :id 1}] {:last-name "Smith" :id 1}]
2 [{:name "Mike" :id 2}]} 2 [{:name "Mike" :id 2}]}
nil nil
{:nauty-list [{:name "Jimmy" :bad true} {:naughty-list [{:name "Jimmy" :bad true}
{:name "Joe" :bad true}] {:name "Joe" :bad true}]
:nice-list [{:name "Jack" :bad false}]}]}] :nice-list [{:name "Jack" :bad false}]}]}]
] ]

23
src/koans/21_group_by.clj
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@ -4,29 +4,32 @@
(meditations (meditations
"To split a collection categorized by keys use the group-by function." "To categorize a collection by some function, use group-by."
(= __ (group-by count ["hello" "world" "foo" "bar"])) (= __ (group-by count ["hello" "world" "foo" "bar"]))
"Sometimes you want to filter a sequence but also keep the predicate." "You can simulate filter + remove in one pass"
(= (get-odds-and-evens '(1 2 3 4 5)) (= (get-odds-and-evens [1 2 3 4 5])
[[1 3 5] [2 4]]) ((partial (juxt filter remove) odd?) [1 2 3 4 5])
[[1 3 5] [2 4]])
"You can also group by a primary key" "You can also group by a primary key"
(= __ (= __
(group-by :id [{:id 1 :name "Bob"} (group-by :id [{:id 1 :name "Bob"}
{:id 2 :name "Mike"} {:id 2 :name "Mike"}
{:id 1 :last-name "Smith"} ])) {:id 1 :last-name "Smith"} ]))
"but be careful when you group by non primary key" "But be careful when you group by non-required key"
(= {"Bob" [{:name "Bob" :id 1}], "Mike" [{:name "Mike" :id 2}], __ [{:last-name "Smith" :id 1}]} (= {"Bob" [{:name "Bob" :id 1}]
"Mike" [{:name "Mike" :id 2}]
__ [{:last-name "Smith" :id 1}]}
(group-by :name [{:id 1 :name "Bob"} (group-by :name [{:id 1 :name "Bob"}
{:id 2 :name "Mike"} {:id 2 :name "Mike"}
{:id 1 :last-name "Smith"}])) {:id 1 :last-name "Smith"}]))
"The true power of group-by is using a custom function" "The true power of group-by comes with custom functions"
(= __ (= __
(group-by #(if (:bad %) :nauty-list :nice-list) (group-by #(if (:bad %) :naughty-list :nice-list)
[{:name "Jimmy" :bad true} [{:name "Jimmy" :bad true}
{:name "Jack" :bad false} {:name "Jack" :bad false}
{:name "Joe" :bad true}]))) {:name "Joe" :bad true}])))