71 lines
1.6 KiB
Clojure
71 lines
1.6 KiB
Clojure
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(ns koans.25-threading-macros
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(:require [koan-engine.core :refer :all]))
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(def a-list
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'(1 2 3 4 5))
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(def a-list-with-maps
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'({:a 1} {:a 2} {:a 3}))
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(defn function-that-takes-a-map [m a b]
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(do
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(println (str "Other unused arguments: " a " " b))
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(get m :a)))
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(defn function-that-takes-a-coll [a b coll]
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(do
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(println (str "Other unused arguments: " a " " b))
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(map :a coll)))
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(meditations
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"We can use thread first for more readable sequential operations"
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(= __
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(-> {}
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(assoc :a 1)))
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"Consider also the case of strings"
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(= __
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(-> "Hello world"
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(str ", and moon")
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(str ", and stars")))
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"When a function has no arguments to partially apply, just reference it"
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(= __
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(-> "String with a trailing space "
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clojure.string/trim))
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"Most operations that take a scalar value as an argument can be threaded-first"
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(= __
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(-> {}
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(assoc :a 1)
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(assoc :b 2)
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(assoc :c {:d 4
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:e 5})
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(update-in [:c :e] inc)
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(get-in [:c :e])))
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"We can use functions we have written ourselves that follow this pattern"
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(= __
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(-> {}
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(assoc :a 1)
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(function-that-takes-a-map "hello" "there")))
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"We can also thread last using ->>"
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(= __
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(->> [1 2 3]
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(map inc)))
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"Most operations that take a collection can be threaded-last"
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(= __
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(->> a-list
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(map inc)
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(filter even?)
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(into [])
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(reduce +)))
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"We can use funtions we have written ourselves that follow this pattern"
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(= __
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(->> a-list-with-maps
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(function-that-takes-a-coll "hello" "there")
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(into []))))
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